Method and apparatus for altering biomechanics of articular joints

ABSTRACT

Pathology of the human knee can arise from excessive and/or uneven loading of regions within the joint. Methods and apparatus are disclosed that enable displacement of soft tissue around the knee, without displacing or severing bone thereby altering the mechanical load distribution within the joint in a less invasive manner than previous techniques.

RELATED APPLICATIONS

This application is a continuation application of U.S. Nonprovisionalpatent application Ser. No. 15/017,098, filed Feb. 5, 2016; whichapplication was a continuation of U.S. Nonprovisional patent applicationSer. No. 13/843,128, filed on Mar. 15, 2013 (now U.S. Pat. No.9,278,004); which application was a U.S. Nonprovisional PatentApplication of and claims priority to U.S. Provisional PatentApplication Ser. No. 61/620,756, filed on Apr. 5, 2012 and U.S.Provisional Patent Application Ser. No. 61/695,406, filed on Aug. 31,2012; U.S. Nonprovisional patent application Ser. No. 13/843,128 wasalso a Continuation-in-Part of U.S. Nonprovisional patent applicationSer. No. 12/870,462, filed on Aug. 27, 2010 (now U.S. Pat. 8,597,362),which claims priority to U.S. Provisional Patent Application Ser. No.61/237,518, filed Aug. 27, 2009, and U.S. Provisional Patent ApplicationSer. No. 61/288,692, filed Dec. 21, 2009. Each of these applications isincorporated herein by reference in its entirety. This application isalso related to U.S. Nonprovisional patent application Ser. No.13/002,829 filed on Aug. 27, 2010 (now U.S. Pat. No. 9,795,410).

FIELD OF THE INVENTION

The present invention generally relates to the field of orthopedics. Inparticular, the present invention is directed to an interventionaltechnique and an implant for altering biomechanics within articularjoints to provide a therapeutic effect. More particularly, embodimentsof the present invention are directed to alleviating joint pain andeffects of osteoarthritis in the knee.

BACKGROUND

The human body contains many joints that permit articulation of varyingdegrees between bones. Those that permit free articulation are referredto as diathroses. Examples include the hip, knee, elbow and shoulder. Avariety of connective tissues are associated with the diathroses joints,including intra-articular cartilages that provide cushioning and smoothsliding surfaces, ligaments that provide flexible connections betweenbones and tendons that slide over joints and connect the muscles toprovide motion. When connective tissues are compromised, joint pain andloss of function can result.

One example of compromised connective tissue is osteoarthritis of theknee or knee OA. The knee joint is formed by the articulation of thefemur, patella, and tibia (FIGS. 1A and 1B). Like other freelyarticulating joints, the knee joint is enclosed by a fibrous jointcapsule, lined by a synovial membrane. The inferior surface of thepatella articulates with the femoral surface forming the patellofemoraljoint. The distal end of the femur has two curved articular surfacescalled the medial and lateral condyles. These surfaces articulate withthe medial and lateral tibial condyles, forming the tibiofemoral joint,which flexes and extends the knee. Two fibrocartilagenous discs (i.e.,menisci) lie between the tibial and femoral condyles to compensate forthe incongruence of the articulating bones. Because the distal end ofthe femur is curved and asymmetric in shape, the knee joint not onlyflexes and extends like a hinge, but it also slides and rotates duringflexion, resulting in a complex motion for the joint.

Knee OA is one of the most common causes of disability in the UnitedStates. OA is sometimes referred to as degenerative, or wear and tear,arthritis. OA is characterized by the breakdown of the articularcartilage within the joint. Over time, the cartilage may wear awayentirely, resulting in bone-on-bone contact. Since bones, unlikecartilage, have many nerve cells, direct bone contact can be verypainful to the OA sufferer. In addition to the pain and swelling, the OAsufferer can experience a progressive loss of mobility at the kneejoint. This is due to loss of the joint space, where the articularcartilage has completely worn away.

Biomechanics of Knee

The normal gait cycle of a human is shown in FIG. 2. The gait cyclebegins when one foot contacts the ground and ends when that footcontacts the ground again. Thus, each cycle begins at initial contactwith a stance phase and proceeds through a swing phase until the cycleends with the limb's next initial contact.

The stance phase accounts for approximately 60 percent, and the swingphase for approximately 40 percent, of a single gait cycle. Each gaitcycle includes two periods when both feet are on the ground. The firstperiod of double limb support begins at initial contact, and lasts forabout the first 10 to 12 percent of the cycle. The second period ofdouble limb support occurs in about the final 10 to 12 percent of stancephase. As the stance limb prepares to leave the ground, the oppositelimb contacts the ground and accepts the body's weight. The two periodsof double limb support account for 20 to 24 percent of the gait cycle'stotal duration.

OA can affect all three compartments of the joint—medial, lateral andpatella-femoral. Varus and valgus orientation of the lower extremity(defined as looking at the tibia from the knee towards the ankle) iscommonly referred to as how-legged (varus) and knock-kneed (valgus)(FIG. 3). Normal alignment of the tibia is in mild varus relative to thevertical.

Excessive loading of the articular cartilage may occur due to obesity,joint misalignment or a combination of such factors. Overly varusalignment can lead to osteoarthritis in the medial compartment whilevalgus alignment can lead to osteoarthritis in the lateral compartment.

In patients suffering from patellofemoral OA, excessive compressiveforces on the patello-femoral cartilage can cause pain and cartilagedegeneration. Such excessive compressive forces are often generatedduring stair climbing. Two main moments acting around the knee jointduring stair climbing are the ground reaction force due to the bodyweight and the quadriceps muscle force that acts on the patella throughthe quadriceps-femoris tendon and the patellar tendon.

Currently, various medications are often recommended to reduce theswelling and pain of OA. Other treatments such as weight loss, braces,orthotics, steroid injections and physical therapy may also helpalleviate pain and restore function by strengthening muscles supportingthe joint. However, since articular cartilage is avascular, or lacks ablood supply, repair and growth of adult cartilage is minimal. If thepain or immobility becomes too severe and other therapies do notalleviate the symptoms, surgical interventions become necessary.Surgical treatments include arthroscopy to clean the joint by removingloose fragments, tibial and femoral osteotomy, unicondylar kneereplacement or total knee replacement.

SUMMARY OF DISCLOSURE

Exemplary methods disclosed herein comprise selecting at least one ofthe muscles and connective tissues associated with a joint as targettissue for treatment, and displacing the target tissue without severingthe bones or target tissue, thereby redistributing loading in the jointto achieve a therapeutic effect.

In one implementation, the present disclosure is directed to anapparatus for treating disorders of articular joints, the joint beingsubject to forces exerted by soft tissues disposed proximate to thejoint with the soft tissues forming target tissues for treatment, theapparatus comprising a prosthesis implantable in engagement with atleast one target tissue so as to displace the target tissue sufficientlyto alter the location, angle or magnitude of the forces exerted by thesoft tissues so as to achieve a therapeutic effect in the joint. Theprosthesis includes a fixation portion including bone fixation meansconfigured to be secured in contact with a bone forming the joint at afixation location outside the articular capsule of the joint, and adisplacement portion configured and dimensioned to extend from thefixation portion to engage and displace the soft tissue, thedisplacement portion having an outer surface, wherein the displacementportion outer surface is smooth and free of holes or fixation means, andwherein the fixation portion of the prosthesis is configured to bemounted to the humerus.

In another implementation, the present disclosure is directed to amethod of treating a shoulder joint having first and second bones. Themethod includes fixing a fixation portion of a treatment device to thefirst bone such that a displacement portion of the treatment deviceengages target tissue in a pretreatment location proximate the shoulderjoint; and displacing the target tissue from the pretreatment locationwith the displacement portion of the treatment device by a distance andin a direction selected to provide a therapeutic effect in the shoulderjoint.

In yet another embodiment, the target tissue exerts a force on theshoulder joint in the pretreatment location and the target tissue isdisplaced so as to redirect the force. Additionally, the moment may beincreased by increasing a moment arm through which the force acts on theshoulder joint.

In further embodiments the therapeutic effect comprises at least one ofreducing pain in the shoulder joint or increasing stability of theshoulder joint. Also, the displacing of the target tissue mayredistribute a load on at least one articular surface in the shoulderjoint and the displacement may be in a direction away from the shoulderjoint. Further, the positioning may comprise fixing the fixation portionat a fixation location spaced from the articular surfaces of theshoulder by at least a distance corresponding to a length of a treatmentdevice spanning section between the displacement portion and fixationportion. In some embodiments, the first bone is the humerus.

In some embodiments, the implant is secured on a first side of a jointto displace tissue on the first side of the joint in order to reduce aload on an opposing side of the joint. For example, the implant may besecured on a lateral side of the femur in order to reduce loads in themedial compartment of the knee. Or, the implant may be secured on amedial side of the femur to reduce loads in a lateral compartment of theknee.

In certain embodiments, tissue may be displaced such that a force in afirst direction on one side of the joint is increased, while a secondforce in the first direction on an opposing side of the joint isdecreased. For example, tissue may be displaced on a lateral side of theknee joint to increase the load on the articular surfaces in the lateralcompartment while decreasing the load on the articular surfaces in themedial compartment.

In still further embodiments, connective tissue near a joint isdisplaced such that a moment arm through which the connective tissueacts upon the joint is increased, thereby reducing a load in the joint.An implant may be secured to a bone near the joint such that the implantdisplaces the connective tissue sufficiently to increase the moment arm.

In preferred embodiments, connective tissue near a joint is displacedsufficiently to achieve a therapeutically effective reduction in a loadin the joint. Usually loads will be reduced at least about 5%,preferably at least about 10%, more preferably at least about 15%. Themagnitude of displacement required to achieve these load reductions willvary depending upon the joint, size and condition of the patient, andother factors. In the case of osteoarthritis in the medial and lateralcompartments of the knee, displacement of connective tissue by at leastabout 8 mm, often by at least about 10 mm, will usually be required.

In another exemplary embodiment, a method for treating medialosteoarthritis of the knee comprises laterally displacing the iliotibialband. Such an embodiment may further comprise selecting at least one ofthe muscles and connective tissues associated with a joint as targettissue for treatment, displacing the target tissue without severing thebones or target tissue, the target tissue being displaced in a regionwhere it is not crossing the joint, wherein the displacementredistributes loading in the joint to achieve a therapeutic effect.

Another exemplary method disclosed herein comprises selecting at leastone of the associated muscle and connective tissues surrounding a jointas target tissue for treatment, displacing the target tissue withoutsevering the bones or target tissue, thereby altering the kinematics ofthe joint to achieve a therapeutic effect. In some embodiments thekinematics are altered to redistribute loading in the joint to achievethe therapeutic effect. In other embodiments the kinematics are alteredto reduce loading on the ligaments within the joint to achieve thetherapeutic effect.

One of the exemplary methods disclosed herein comprises selecting atleast one of the associated muscle and connective tissues as targettissue for treatment, displacing the target tissue without severing thebones or target tissue, and redistributing loading in the joint toachieve a therapeutic effect. The apparatus may be completely outsidethe capsule surrounding the joint or may be in contact with the exteriorof the capsule.

Embodiments of the present invention may be applied to virtually anyarticular joint, including but not limited to the knee, shoulder or hip.In addition to the implants and related prosthesis and apparatusdescribed, embodiments of the present invention include methods oftreating joint disorders and methods of installing implants andprostheses for less invasive joint treatments.

By using the implants of the invention, appropriately sized andpositioned as described herein, displacement of targeted connective andmuscle tissues surrounding the joint is accomplished in order to realignforce vectors and/or alter moment arms loading the joint to achievetherapeutic effects without cutting bone and with minimal cutting of theconnective tissues. Alternative and more specific devices andmethodologies are described in more detail herein below.

BRIEF DESCRIPTION OF DRAWINGS

For the purpose of illustrating the invention, the drawings show aspectsof one or more exemplary embodiments of the invention. However, itshould be understood that the present invention is not limited to theprecise arrangements and instrumentalities shown in the drawings,wherein:

FIG. 1A is a front or anterior view of the bones of the right knee jointin a human, illustrating the lateral and medial directions and themedial and lateral compartments of the knee.

FIG. 1B is a sagittal or vertical section of the right knee joint,illustrating the anterior and posterior directions and thepatellofemoral compartment of the knee.

FIG. 2 is a schematic diagram illustrating the human gait cycle.

FIG. 3 is a figure depicting normal knees, bowlegged knees (varusmisalignment) and knock knees (valgus misalignment).

FIG. 4 depicts an exemplary embodiment of a prosthesis according to thepresent invention.

FIGS. 5A-D depict the cross-sectional views of the displacement portionof the prostheses according to one embodiment of the present invention.

FIG. 6 is an anterior view of a right knee illustrating positioning ofanother exemplary embodiment of the present invention for treatinglateral compartment osteoarthritis.

FIG. 7 is an anterior view of a right knee illustrating positioning ofanother exemplary embodiment of the present invention for treatinglateral compartment osteoarthritis.

FIG. 8 is an anterior view of a right knee illustrating positioning ofan exemplary embodiment of the present invention for treatingpatellofemoral osteoarthritis or chondromalacia.

FIGS. 9A-E are views of a an exemplary prosthesis for anteriordisplacement of the patellar tendon in the right knee, wherein 9A is aperspective view, 9B is an anterior (front) view, 9C is a lateral (side)view, 9D is a posterior (back) view and 9E is a cranial (top) view.

FIGS. 10, 11 and 12 are views of prostheses according to alternativeexemplary embodiments of the present invention for anterior displacementof the quadriceps-femoris tendon.

FIG. 13 is an anterior view of a right knee illustrating positioning ofanother exemplary embodiment of the present invention for treatingpatellofemoral osteoarthritis and lateral compartment osteoarthritis.

FIG. 14 is an anterior view of a right knee illustrating positioning ofanother exemplary embodiment of the present invention for treatingpatellofemoral osteoarthritis and medial compartment osteoarthritis.

FIG. 15 is an anterior view of a right knee illustrating positioning ofanother exemplary embodiment of the present invention for treatingpatellofemoral osteoarthritis and medial compartment osteoarthritis.

FIG. 16 is an anterior view of a right knee illustrating positioning ofanother exemplary embodiment of the present invention for treatingpatellofemoral osteoarthritis and lateral compartment osteoarthritis.

FIG. 17 is an anterior view of a right knee illustrating positioning ofanother exemplary embodiment of the present invention for treatingmedial compartment osteoarthritis.

FIGS. 18A-D are views of a prosthesis for lateral displacement of the ITBand in the right knee in accordance with yet another exemplaryembodiment of the present invention, wherein 18A is a perspective view,18B is a lateral view, 18C is an anterior view and 18D is the caudal(bottom) view.

FIG. 19 is a schematic perspective view of an embodiment of the presentinvention incorporating an adjustable capsule between two solid members.

FIG. 20 is a schematic cross sectional view of an embodiment of thepresent invention incorporating an adjustable capsule between two solidmembers.

FIG. 21 is a schematic cross sectional view of an further alternativeembodiment including a multi-chamber capsule between two solid members.

FIG. 22 is a schematic cross sectional view of another alternativeembodiment of the present invention incorporating an adjustablemechanical construct between two solid members.

FIG. 23 is an anterior view of a right knee illustrating positioning ofanother exemplary embodiment of the present invention for treatingmedial compartment osteoarthritis.

FIGS. 24, 25 and 26 are side schematic side views of prosthesesaccording to alternative exemplary embodiments of the present invention.

FIG. 27 is an anterior view of a right knee illustrating positioning ofan alternative exemplary embodiment of the present invention fortreating medial osteoarthritis with an adjustable tensioning device.

FIGS. 28 and 29 are schematic side views of a human knee with prosthesesaccording to embodiments of the present invention, including at least aroller in the displacement portion of the prostheses.

FIG. 30 is an anterior view of the femur of a right knee illustratingpositioning of an alternative exemplary embodiment of the presentinvention for treating medial osteoarthritis with a two piece device.

FIG. 31 is an anterior view of the femur of a human knee illustratingpositioning of another exemplary embodiment of the present invention fortreating medial osteoarthritis with a multi-layered device.

FIG. 32 is an anterior view of the femur of a human knee illustratingpositioning of an alternative exemplary embodiment of the presentinvention for treating medial osteoarthritis with a multi-layereddevice.

FIGS. 33-43, 45, 47-49 are partial cross-sectional views of the distalfemur of a human knee (oriented horizontally) illustrating alternativeexemplary embodiments of the present invention.

FIGS. 44A-B are exemplary embodiments of the bearing unit of a two-partdevice.

FIG. 46 is an exemplary embodiment of a composite bearing unit of atwo-part device.

FIGS. 50A-E and 51 are views of prostheses for lateral displacement ofthe IT Band in the right knee in accordance with other exemplaryembodiments of the present invention, wherein FIG. 50A is a perspectiveview, FIG. 50B is a top view, FIG. 50C is a side view as seen from theanterior side of the implant, and FIG. 50D is a side view as seen fromthe posterior side of the implant. FIGS. 50E and 51 are views of aprosthesis for lateral displacement of the IT Band in the right knee inaccordance with yet another exemplary embodiment of the presentinvention, wherein 50E is a cross-sectional view of the implantsectioned through A-A, and 51 is a cross-sectional view of the implantsectioned through B-B of FIG. 50B.

FIG. 52 shows the cross-sectional views of two implants of the presentinvention.

FIGS. 53A-C are views of a prosthesis for lateral displacement of the ITBand in the right knee in accordance with yet another exemplaryembodiment of the present invention, wherein 53A is a top view, 53B is across-sectional view of the implant placed on the lateral condyle, and53C is a cross-sectional view of the implant sectioned through A-A.

FIG. 54 is a prosthesis for lateral displacement of the IT Band in theright knee in accordance with yet another exemplary embodiment of thepresent invention,

FIG. 55A-C are views of a prosthesis to improve cosmesis in accordancewith yet another exemplary embodiment of the present invention.

FIGS. 56A-D are views of an exemplary embodiment of an inserter devicefor implanting the prosthesis of the present invention.

FIGS. 57A-B are views of an exemplary embodiment of an inserter devicefor implanting the prosthesis of the present invention.

FIGS. 58A-B are views of an exemplary embodiment of a dissection devicefor implanting the prosthesis of the present invention.

FIGS. 59A-H are views of an exemplary surgical procedure to implant theprosthesis of the present invention.

DETAILED DESCRIPTION

Utilizing embodiments of the present invention, joint conditions thatresult from or exacerbate unbalanced force distribution through thejoint may be addressed by interventional techniques involving aredistribution of forces exerted on the joint without the need forhighly invasive surgeries requiring significant trauma to the joint andassociated muscle and connective tissues. Redistribution of forceswithin the target joint in accordance with embodiments described hereinmay thus provide pain relief or slow down articular cartilagedegeneration or enhance cartilage regeneration.

In some embodiments of the invention, increased forces can beselectively applied to one side of a joint by routing select muscle,tendons, ligaments, and/or other connective tissues (target tissues)around a longer or more angled path, thus increasing the magnitude,altering the effective direction, and/or changing the moment arm offorces exerted by such muscles or tissues on the joint. This may beaccomplished, for example, by appropriately shaped implants that may bepositioned to displace selected target tissues relatively non-invasivelycompared to current surgical techniques for addressing such conditions.The amount of displacement of the target tissue may not need to be largein order to provide a substantial therapeutic effect on the targetjoint. For example, in the knee, depending upon the nature of thedisease and the size and geometry of a particular patient's joint,displacements of greater than about 5 mm up to about 30 mm may besufficient, with displacements in the range of about 10 mm to about 30mm also suitable, or more specifically about 10-20 mm.

Exemplary embodiments of the invention described herein are particularlydirected to treatment of the human knee, although the principles of theinvention may be applied to other joints as described in the copendingparent application of the present application, which as stated above isincorporated by reference herein. In general, it will be appreciated bypersons of ordinary skill in the art that specific features described inconnection with one exemplary embodiment may be incorporated in otherexemplary embodiments unless otherwise noted. The exemplary embodimentsdescribed are thus included to illustrate features of the invention, notlimit it.

As used herein, “therapeutic effect” means an effect on a treated jointthat reduces forces acting on the articular surfaces, reduces wear,lessens pain or provides another positive outcome for the patientwhether across the joint as a whole or in particular compartments of theknee. “Therapeutic effect,” however, does not imply, and should not beunderstood as requiring, any specific, quantified outcome other than asstated above.

As used herein, in humans, dorsal refers to the back of an organism andventral to the belly. Cranial refers to the head end and caudal to thetail end. In humans, anterior is used to indicate the ventral surfaceand posterior to indicate the dorsal surface. Superior means toward thehead and inferior toward the feet. Proximal refers to the end of astructure nearest a major point of reference and distal to the endfurthest from a point of reference. The point of reference is usuallythe origin of a structure (such as a limb). Proximal and distal arerelative terms. Medial means nearer the midline of the body and lateralmeans further from the midline. Superficial refers to structures nearerthe skin, and deep to structures further away from the skin. A sagittalplane divides the body into right and left (or medial and lateral)parts. A frontal (or coronal) plane passes from right to left anddivides the body into dorsal and ventral (or posterior and anterior)parts. A transverse plane (or cross section) passes perpendicular to thelong axis of the body and divides the body into cranial and caudal (headand tail) portions.

While illustrated in FIGS. 1A and 1B for the sake of clarity, persons ofordinary skill in the art will understand the location and anatomy ofthe compartments of the knee, commonly referred to as the MedialCompartment (MC), Lateral Compartment (LC) and PatellofemoralCompartment (PFC). Also illustrated in FIGS. 1A and 1B are anatomicaldirections relative to the knee joint as referenced herein.

Implants according to embodiments of the present invention may beconfigured and secured in a variety of ways as described below in moredetail with respect to exemplary embodiments. However, in general, andwith reference to FIG. 4, prostheses or implants according toembodiments of the invention will, in preferred embodiments, comprise afixation portion 12 that provides means for securing or anchoring theprosthesis, such as holes 13 for bone screws 15, and a displacementportion 14 configured and dimensioned to displace the target tissue(s)from a pretreatment path as described herein. Other means for securingthe fixation portion may include bone ingrowth surfaces, barbs, bonecement and other devices known in the art for securing implants to bone.The fixation and displacement portions may be separated by a spanningsection 16 that permits those portions to be separated from each otheras appropriate to accommodate the anatomical structures at the locationof treatment and fixation. The displacement portion 14 may be providedwith a bearing member 17 of the same or a different material than theunderlying substrate. In some embodiments, again depending on anatomicalstructures and treatment requirements, two or more of the displacementand fixation portions and spanning section may be merged in whole or inpart or may overly one another.

Depending on the mechanical load on the implant, and the choice ofmaterial or materials used to fabricate the implant, thickness of thefixation portion (for example; T₁ in FIG. 9E, T₂ in FIG. 18C) of theimplant typically ranges from about 2.0 mm to 8.0 mm, more typicallyfrom about 2.5 mm to 6.0 mm, and may be from about 3.0 mm to 4.5 mm. Thethickness of the fixation portion of the implant (for example; T₃ inFIG. 9E) may be uniform throughout the implant or may vary across theimplant. Regions of the fixation portion under higher mechanical loadmay be thicker than regions under lower mechanical loads. The thicknessof the fixation region may also be selected to ensure that thescrew-heads used to fix the implant do not protrude over the surface ofthe implant. Examples of thickness T₁, T₂ etc. are shown in FIGS. 9C, 9Eand 18C.

The spanning section may have thickness similar to that of the fixationportion. Persons of ordinary skill in the art will appreciate that aprincipal consideration for spanning section is sufficient structuralintegrity to maintain the displacement portion at the desired treatmentposition. In the displacement portion, displacement distance andthickness may be considered separately. Displacement distance is thedistance by which the bearing surface of the displacement portiondisplaces the target tissue beyond the natural anatomical track of thetarget tissue, in other words, the displacement of tissue created by theimplant. Depending on the particular geometry of the implant, thethickness of the displacement portion may or may not be related to thedisplacement distance. For example, in an implant with a convex or spoonshaped displacement portion (see, e.g. FIG. 18), or one with adisplacement portion that is cantilevered at an angle or stepped into adifferent plane from the fixation portion or spanning section, thethickness of the material may be substantially less than the overalldisplacement distance. For example, a material thickness of 4 or 5 mm inthe displacement portion may provide sufficient structural integrity fora displacement distance of 25 to 30 mm depending on the materialselected. In one embodiment, displacement of the target tissue resultsin the decrease in the mechanical load on the articular cartilage in thetarget joint by at least 5%, more preferably by at least 8%, mostpreferably by at least 10%. Unloading as defined here refers to decreasein contact forces, either peak forces or average forces, either measuredor calculated, during a normal gait cycle, stair climbing, running,jogging or any other physical activity which results in mechanicalloading of articular cartilage in a joint.

The displacement distance provided by the displacement portion of theimplant may typically range from greater than about 5 mm to about 30 mm.Of course, the actual displacement distance will depend upon the jointbeing treated, the location and physical characteristics of the targettissue, the severity of disease, and other factors. In some embodiments,displacement distance across the displacement portion may vary. Asfurther examples of how displacement distance and thickness may relate,the displacement portion may be in contact with the underlying tissueand the target soft tissue is displaced by a distance equivalent to thethickness of the displacement portion; thus displacement distance wouldequal thickness in such an embodiment. In other embodiments, thedisplacement portion may be elevated above the underlying tissue and thetarget soft tissue is displaced by a distance greater than the thicknessof the displacement region; thus displacement distance is greater thanthickness.

Persons of ordinary skill in the art will thus appreciate that a furtherdimension to be considered is the depth (D) of the implant that governsthe magnitude of tissue displacement, i.e., the perpendicular distancefrom an outer most point on the bearing surface to a point on thefixation surface, that is, the surface of the fixation portionconfigured to face the fixation site. Typically, depth (D) will bemeasured as perpendicular to a plane tangent to an outer most point onthe bearing surface, between that plane and a point on the fixationsurface that defines the location of fixation to the bone, for example acenterline of the fixation element(s) such as screw holes, provided inthe fixation portion. Examples of depth (D) are shown in FIGS. 9B, 9Eand 18C.

In alternative embodiments, components of the prosthesis may be acompliant material such as an elastomer, capsules filled with water,saline, silicone, hydrogels, etc. Embodiments with compliant portionscould be placed in a deflated state and then inflated to the appropriatethickness. Alternatively, bearing members may be filled with otherflowable materials including beads or other particles made of metal,polymer, or foam material, optionally in a liquid medium, which conformto the adjacent bone or tissue surfaces. Thixotropic materials, such ashydrogels derived from hyaluronic acid, change their mechanicalproperties as shear stress is applied to them. An implant filled withsuch materials could be made to change the amount of displacement thatit provides based on the shear stress that it sees from overlying targettissues at various points in the gait cycle. Implants may be coated withmaterials to reduce friction such as hydrophilic coatings orpolytetrafluoroethylene (PTFE) coatings. Additionally or alternatively,the prosthesis may be adjustable to allow the dimensions such asthickness of the prosthesis to be adjusted during surgery or any timeafter surgery.

Rigid or substantially rigid prostheses according to embodiments of theinvention described herein could be made of known bone-compatibleimplant materials such as titanium or stainless steel. Biocompatiblepolymers, ceramics, and other materials may also be used. The bearingsurface of the prostheses should be designed to minimize negativeeffects of movement of the connective tissues across the implantsurface, e.g. comprising a smooth, atraumatic, low-friction material,coating or surface treatment. Such prostheses could be implantedarthroscopically or using a mini-open or open surgical approach.

In various alternative embodiments, the displacement portion and thefixation portion of prostheses according to the invention may be ofunibody construction, or may be formed of two or more parts depending ondesired function. For example, the fixation portion may be stainlesssteel or titanium textured to enhance bony ingrowth and solid screwfixation, while the displacement portion could be made of a differentmaterial, for example, pyrolytic carbon to enhance the ability ofoverlying tissues to slide across the implant, or PTFE, silicone orother low-friction polymer with suitable wear characteristics to providea softer bearing surface. In this regard, the displacement portion maycomprise a separate bearing member with a bearing surface on which thetarget tissue bears. Alternatively the bearing surface may be formed asan integral part of the displacement portion. In further alternatives,the displacement portion could be comprised of a substrate of onematerial with an overlying layer forming the bearing member. Thesubstrate could be either attached to or contiguous with the fixationportion. In other embodiments, the fixation portion of the implant mayhave a relief feature to minimize contact with the underlying bone,thereby minimizing disruption of the periosteal layer.

Generally, the bearing member and/or bearing surface in embodiments ofthe invention will be hard and smooth, made from materials such aspolished pyrolytic carbon, steel, or titanium, or coated or covered witha lubricious material, such as PTFE. However, in embodiments whererelative motion is provided for within the prosthesis itself, such as inexemplary embodiments described herein below, the bearing surface may bedesigned to encourage adhesion and ingrowth of the connective tissueonto this surface. For example, such a surface may be porous, roughened,or configured with openings into which bone or scar tissue may grow toenhance adhesion.

In some embodiments, the implant could be anchored to the underlyingbone with suitable fasteners such as screws. Depending on the locationand surgical need, unicortical screws, bicortical screws, cancellousscrews, cannulated screws, polyaxial screws, screws that lock into theimplant etc. may be used. In some embodiments, the screw holes may belocking threads or other locking features. In other embodiments, thescrews holes may be oriented in different directions to improve thestability of the anchored implant. In alternate embodiments, differenttypes of screws may be used in different regions of the implant. Forexample, cortical screws may be used in the region of the implant incontact with the femoral shaft while cancellous screws may be used inanother part of the implant in contact with femoral condyle. Dependingon patient anatomy and geometry of a specific implant, it may bedesirable to provide supplemental fixation (such as cancellous bonescrews) in the spanning section.

As discussed above, lateral condylar osteoarthritis may be caused byexcessive loading of the lateral condyle. Excessive loading may resultfrom obesity or joint misalignment (valgus or knock knees). By mediallydisplacing the medial muscles or tendons like the sartorius and gracilismuscle or tendon, the moment arm of the muscle or tendon as it crossesthe joint may be increased, thereby redistributing the forces within thejoint, and reducing the load on the lateral condyle. Other muscles andtendons around the knee that contribute to the medial stability of theknee may also be displaced to achieve a similar therapeutic effect.

FIGS. 6 and 7 show exemplary embodiments of the present invention formedial displacement of the medial muscles or tendons around the knee.FIG. 6 depicts a first embodiment of an implant 100 anchored on themedial side of the tibia. The definitions of the dimensions (forexample, L, W, T, D etc.) of the implant in FIG. 6 are the same as thosefor the implant in FIG. 9. Fixation portion 112 of the implant is usedto anchor the implant, e.g. with screws 113, and displacement portion114 displaces the sartorius and/or gracilis tendon medially. Thefixation portion could be attached to the tibia adjacent to theattachment point of the patellar tendon and the tibia or it could belocated more cranial or caudal to the attachment point. In one exemplaryembodiment of implant 100, the width of the fixation portion 112 rangesfrom about 10 mm to 25 mm, more specifically from about 12 mm to 20 mm,and in certain embodiments from about 14 mm to 18 mm. The length of thefixation portion 112 for implant 100 may be in the range of about 20 mmto 50 mm, more specifically from about 25 mm to 45 mm, and in certainembodiments about 30 mm to 40 mm. Spanning section 116 would beconfigured to transition from fixation portion 112 mostly parallel tothe medial side of the tibia to displacement portion 114, which, asstated above, is configured and dimensioned to displace the sartorius orgracilis tendon medially.

The displacement of the target tissue can be altered by changing thelength, curvature and angle of the spanning section 116, with anembodiment such as implant 100, each affecting the overall depth of theimplant. For example, the angle between the displacement portion 114 andthe fixation portion 112 (angle as measured at the intersection of thecenter line axes of the two portions in the top view of the implantsimilar to angle α shown in FIG. 9A) may range from about 80 degrees to135 degrees, more specifically about 85 degrees to 120 degrees, and insome from about 90 degrees to 110 degrees. The inferior edge of thespanning section 116 can also be curved to minimize or eliminate anycontact with the anterior edge of the sartorius or gracilis tendon andcould be configured to avoid the attachment region of the tendons to thetibia. The displacement of the target tissue may also be altered bychanging the cross-section of the displacement portion. The width of thedisplacement portion 114 may range from about 10 mm to 25 mm, morespecifically about 12 mm to 20 mm, and in some embodiments about 14 mmto 18 mm. The length of the displacement portion 111 may range fromabout 20 mm to 50 mm, more specifically about 25 mm to 45 mm, and insome embodiments about 30 mm to 40 mm. The length and width should besufficient to provide adequate support of the target tissue over itsrange of motion without excessive or extra material. By appropriateadjustment of these dimensions a person of ordinary skill in the art mayconfigure the implant with a depth to provide displacement of the targettissue in the range of about 5 mm to 30 mm.

Another embodiment is shown in FIG. 7, which depicts implant 200anchored on the medial side of the femur. The definitions of thedimensions of the implant (for example, L, W, T, D etc.) in FIG. 7 arethe same as those for the implant in FIG. 18. Fixation portion 212 ofthe implant is used to anchor the implant and displacement portion 214displaces the sartorius and/or gracilis tendon medially. Displacementportions 114 and 214 may be adjusted to provide appropriate displacementto achieve a therapeutic effect as described. In an exemplaryembodiment, displacement portion 214 is offset medially relative tofixation portion 212 so as to extend around the medial facet of thefemoral condyle. The displacement portion 214 may be generally parallelwith the fixation portion 212, and be interconnected by a spanningsection 216 which extends at an angle medially and caudally fromfixation portion 212. The spanning section extends the displacementportion out medially to achieve a desired displacement. Additionally,spanning section 216 is configured and dimensioned to reduce contact orimpingement with bone or soft tissue underneath the displacement portion(e.g.; joint capsule, tibial collateral ligament etc.). The fixationportion 212 may lie in a place which is generally parallel to thedisplacement portion 214, with both configured to lie on the medialaspect of the bone when implanted. Alternatively, displacement portion214 may be in a plane which is nonparallel to that containing thefixation portion; for example the fixation portion may be configured anddimensional for attachment to a more anterior aspect of the tibia whilethe displacement portion is configured to face more medially with thespanning section, bridging the region between the displacement portionand fixation portion.

The width of implant 200 as measured in the anterior-posterior directionmay vary depending on anatomical conditions and other factors asdetermined by the surgeon. For example, the width of implant 200 infixation portion 212 could be constant while the width of thedisplacement portion 214 could vary along its length to cover the medialfacet of the condyle. The width of the spanning section 216 would bridgethe difference in widths between the fixation portion and thedisplacement portion. In exemplary embodiments, the width of fixationportion 212 may range from about 10 mm to 40 mm, more specifically about15 mm to 35 mm, and in some embodiments about 20 mm to 30 mm. The lengthof the fixation portion 212 may range from about 20 mm to 60 mm,specifically about 30 mm to 50 mm, and in some embodiments about 35 mmto 45 mm. The width of the displacement portion 214 may range from about40 mm to 70 mm, more specifically about 45 mm to 65 mm, and in someembodiments about 50 mm to 60 mm. The length of the displacement portion212 may range from about 40 mm to 70 mm, more specifically about 45 mmto 65 mm, and in some embodiments about 50 mm to 60 mm.

Patellofemoral osteoarthritis may be caused by excessive compressiveload on the patella. By anteriorly displacing the patellar tendon or thequadriceps-femoris tendon the compressive load on the patella may bereduced. While it has been recognized that such displacement of thepatellar tendon may have benefits, existing approaches have sufferedfrom certain difficulties. For example, it has been suggested that aprosthetic implant could be inserted and anchored beneath the patellartendon cranially from the tendon insertion point on the tibia. However,because the tendon overlies this area, obtaining access and clearvisualization of the anchoring site can be difficult. Moreover, the areaof the bone available to insert screws is limited, requiring the screwsto be placed closer together than would be ideal for secure anchoring.Further, anchoring a device to the tibia at this location risks damagingthe patellar tendon and other ligaments and tendons which insert intothe tibia nearby. In addition, such an implant can cause a cosmeticallyunattractive bump. In the present invention, by contrast, implants maybe configured such that the displacement portion of the implant isseparated from the fixation portion of the implant. With thedisplacement portion positioned under the target tissue (e.g. patellartendon), the fixation portion of the implant may be configured to beaffixed to the bone at a location which can securely fix the implant inplace, is accessible to the surgeon, is not covered by the targettissue, and is separated from tendon insertion points and otheranatomical features. The implant may have a spanning section shaped anddimensioned to bridge the distance between the fixation portion and thedisplacement portion. The implants may be configured to move the tendonanteriorly or medially or anterior-medially or laterally orantero-laterally. This may be accomplished by making one side (lateralor medial) of the displacement surface higher than the other, and/or byforming a track with ridges on one or both sides of the bearing surfaceto urge the tendon in a lateral or medial direction.

FIG. 8 shows such an exemplary embodiment of the present invention fordisplacement of the patellar tendon. Implant 300 is anchored on themedial side of the tibia. Fixation portion 312 of the implant is used toanchor the implant and displacement portion 314 displaces the patellartendon. Advantageously, the fixation portion is separated from thedisplacement portion by spanning section 316 so that the fixationportion may be shaped and dimensioned to optimize anchoring, holes 315for screws 313 may be more numerous and separated further apart, and thelocation on the bone for anchoring may be more easily accessed andvisualized by the surgeon. Additionally, the fixation portion may beconfigured to minimize skin irritation. For example, by configuring thedisplacement portion 314 to rest on the bone underneath the patellartendon, the load on the device could be distributed such that the stresson the fixation portion 312 is reduced. Reduction in the stress on thefixation portion 312 would enable that portion to have a lower profileor lower thickness, thereby reducing any skin irritation and achievingother attendant benefits of a smaller profile. In an alternativeembodiment, the displacement portion may be elevated from the underlyingbone such that only the most lateral region 303 of the implant is incontact with the tibia, thereby minimizing any damage to the periosteallayer.

FIGS. 9A-E depict an exemplary prototype of implant 300 for treatingpatellofemoral osteoarthritis and/or patellar maltracking for the rightknee as depicted in FIG. 8. Implant 300 has a fixation portion 312having one or more holes 315 for receiving screws for anchoring theimplant to bone. Fixation portion 312 is generally straight andelongated, being configured for positioning in general alignment withthe tibial shaft on the medial or anterior-medial side of the tibia.Holes 315 are preferably positioned in approximate alignment with alongitudinal centerline of fixation portion 312. Displacement portion314, is configured and dimensioned to be positioned under the patellartendon cranially separated from the insertion point of the tendon in thetibia. The displacement portion 314 is configured to atraumaticallyengage the tendon and displace it anteriorly relative to the tibia. Thedisplacement portion 314 has a length in the lateral-medial directionselected to accommodate the full width of the tendon so that the tendonremains engaged along its entire width as it slides on the displacementportion. Displacement portion 314 preferably has a convex curvature onits outer tissue-engaging surface (bearing surface), preferably beingcurved at least around an axis generally parallel to the tibial shaft,usually being curved also around an axis perpendicular to the tibialshaft, and more preferably being spherical or partially spherical.Displacement portion 314 has a width in the caudal-cranial direction isselected so that it does not interfere with the patella or engage theinsertion point of the tendon, typically being less than its length. Aspanning section 316 interconnects fixation portion 312 and displacementportion 314. Spanning section 316, in the embodiment illustrated,extends cranially and laterally from fixation portion 312 todisplacement portion 314, forming a curve of about 90° about adorsal-ventral axis. Where fixation portion 312 is configured forattachment to a more medial aspect of the tibia, spanning section 316will extend ventrally as well as cranially and laterally from fixationportion 312, preferably being curved about an axis generally parallel tothe tibial shaft. Displacement portion 314 appropriately displaces thepatellar tendon in cooperation with the fixation portion 312 andspanning section 316.

Displacement of the target tissue can be altered by changing the length,curvature and angle of the spanning section among other features. Forexample, the angle α between the displacement portion 314 and thefixation portion 312 (as measured at the intersection of the center lineaxes of the two portions in the top view of the implant in FIG. 9A) mayrange from about 80 degrees to 135 degrees, more specifically from about85 degrees to 120 degrees, and in some embodiments about 90 degrees to110 degrees. The width W₁ of the fixation portion 312 will be largeenough to span a substantial portion of the width of the tibia and toaccommodate one or more screw holes of sufficient size, ranging fromabout 10 mm to 25 mm, more specifically about 12 mm to 20 mm, and insome embodiments about 14 mm to 18 mm. The length L₁ of the fixationportion 312 will be selected to accommodate a sufficient number of screwholes in the cranial-caudal direction along the tibia, usually at leasttwo and in some embodiments up to five or more, and may range from about20 mm to 50 mm, more specifically about 25 mm to 45 mm, and in someembodiments about 30 mm to 40 mm. The width W₂ of the displacementportion 314 is selected to provide a broad area of contact with thetendon to spread the force and reduce wear, while not interfering withthe patella or the tendon insertion point throughout the full range ofjoint motion. Width W₂ may thus range from about 10 mm to 25 mm, morespecifically about 12 mm to 20 mm, and in some embodiments about 14 mmto 18 mm. The length L₂ of the displacement portion 314 is selected sothat the displacement portion extends under the full width of the tendonso that the entire width of the tendon remains in engagement anddisplaced the desired amount throughout the range of joint motion.Length L₂ may thus range from about 20 mm to 50 mm, more specificallyabout 25 mm to 45 mm, and in certain embodiments about 30 mm to 40 mm.Implant depth D, along with the radius of curvature R₁ of the outersurface of displacement portion 314, shown in FIG. 9E, are selected tooptimize tendon displacement throughout the range of joint motion.Radius of curvature R₁ is usually 20-35 mm, more preferably 22-33 mm,and most preferably 25-30 mm. For average patient anatomy, an overallimplant depth (D), shown in FIGS. 9B and 9E, as measured from theoutermost surface of displacement portion 314 to the centerline of thescrew holes in fixation portion 312, would be in the range of 10-45 mmin order to provide target tissue displacements in the ranges citedhereinabove to achieve a therapeutic effect.

The inferior edge 304 of the spanning section 316 can also be curved tominimize or eliminate any contact with the medial edge of the patellartendon. The superior surface edge 305 of the displacement portion 314can be curved to allow for easy motion of the patellar tendon duringflexion as well as to vary the displacement of the patellar tendonduring flexion by varying the region of the implant surface in contactwith the tendon at higher flexion angles. In one exemplary embodiment,implant 300 is placed on the medial side of the distal tibia such thatfixation portion 312 is substantially aligned with the tibial shaft, thespanning section 316 is positioned to minimize contact with the medialedge of the patellar tendon, and the displacement portion 314, extendinglaterally from the spanning section, is substantially parallel to thetibial plateau.

FIGS. 10, 11 and 12 show exemplary embodiments of implants according tothe present invention for displacement of the quadriceps-femoris tendon.FIG. 10 depicts implant 400 anchored on the lateral side of the femurusing one or more fixation screws 413. Holes (not visible in thefigures) extending through fixation portion 412 for receiving screw(s)413 are oriented in a lateral-medial direction so screw(s) 413 may beinserted into a lateral aspect of the femur. Displacement portion 414extends generally orthogonally in a medial direction from fixationportion 412 so as to extend across an anterior aspect of the femur underthe quadriceps-femoris tendon. A spanning section (described below) mayinterconnect displacement portion 414 and fixation portion 412,extending anteriorly and medially from the fixation portion andpreferably being curved about an axis generally parallel to the femoralshaft. Fixation portion 412 of implant 400 is used to anchor the implantand displacement portion 414 displaces the tendon. Supplementaryfixation 418 may be provided at the opposite end of displacement portion414 and may also include additional anchoring features like screw holes,spikes etc. In other embodiments, the implant may be anchored on themedial side without a substantial change other than mirroring.

FIGS. 11 and 12 depict implants 420 and 430 with the fixation portions422 and 432 that are displaced, caudally and cranially respectively,from the tendon-displacing displacement portions 424 and 434.Displacement portions 414, 424 and 434 may be designed to be in contactwith the underlying bone or could be partially or wholly elevated so asto avoid contact with the underlying bone, thereby not disrupting theperiosteal layer. Implants 420 and 430 also may have supplementalfixation 418, which may also include additional anchoring features likescrew holes, spikes etc. In some embodiments, the implant is anchoredonly on one side (medial or lateral), thereby allowing the implantationprocedure to be performed by a single incision. In other embodiments,when supplemental fixation 418 is employed, the opposite side may alsobe anchored using a percutaneous technique, for example, by using apercutaneous screw.

As with other embodiments described herein, the displacement of thetarget tissue can be altered by changing the length, curvature and angleof the spanning section and/or dimensions of the displacement andfixation portions as appropriate for specific patient anatomy.Displacement portions 414, 424 and 434 may be configured to move thetendon anteriorly or medially or anterior-medially or laterally orantero-laterally. This may be accomplished by making one side (lateralor medial) of the displacement surface higher than the other, and/or byforming a track with ridges on one or both sides of the bearing surfaceto urge the tendon in a lateral or medial direction. The inferior regionof the displacement portions may be contoured or concave tosubstantially conform to the curved anterior surface of the femur. Thesuperior surface or the hearing surface on the displacement portion alsomay be contoured to have a curved convex surface in contact with thetarget soft tissue. For example, the cross-sectional view of thedisplacement portion may look like a semi-circle or a semi ellipse(FIGS. 5A-D).

The displacement portion 424 and 434 may be generally orthogonal withrespect to fixation portion 422 and 432. The connecting spanningsections 426 and 436 could extend at an angle medially and anteriorlyfrom fixation portions 422 and 432. The spanning section extends thedisplacement portion out anteriorly to achieve the necessarydisplacement. The spanning section may also extend more caudally orposteriorly to the displacement section to avoid any connective tissueattachment points. The spanning sections may also comprise adjustablemechanisms (e.g. a pin or hinge) to movably or pivotably alter theorientation or angle between the two parts to achieve the appropriatelevel of tissue displacement; exemplary embodiments of which aredescribed herein below. The width of the displacement portions 414, 424and 434 may range from about 10 mm to 40 mm, more specifically about 15mm to 35 mm, and in some embodiments about 20 mm to 30 mm. The length ofthe displacement region would typically substantially cover the width ofthe femoral shaft. Overall depth (D) in exemplary embodiments ofimplants 400, 420 and 430, in this case as measured from an outer mostsurface of the displacement portion to the mid-line of the fixationportion passing through at least one screw hole or fixation elementwould be in the range of about 10-45 mm, to achieve displacements asdescribed herein for average patient anatomy.

In other embodiments of the present invention, an apparatus for treatingdual compartment osteoarthritis of the knee are disclosed. For example,embodiments of the present invention may be configured to treat medialand patellofemoral osteoarthritis, or lateral and patellofermoralosteoarthritis. FIGS. 13 and 14 depict exemplary embodiments of tibialimplants 500 and 530 to treat dual compartment osteoarthritis. FIGS. 15and 16 depict exemplary embodiments of femoral implants 600 and 630 totreat dual compartment osteoarthritis. These embodiments arealternatives to placing separate implants, also disclosed herein, totreat dual compartment osteoarthritis. The dimensions of the implantsfor treating dual compartment osteoarthritis would preferably be similarto the dimensions of the implants to treat single compartmentosteoarthritis described in connection with exemplary embodiments of thepresent invention discussed herein. The fixation portion of a dualcompartment treatment implant may be subject to higher mechanical forcescompared to single compartment treatment implants. To withstand thehigher mechanical loads, the fixation portion may preferably be thicker,wider or longer as may be selected by a person skilled in the art basedon the teachings contained herein.

In FIG. 13, fixation portion 512 is used to anchor implant 500 on thetibia, anterior displacement portion 514 displaces the patellar tendonand medial displacement portion 524 displaces the medial sartoriusand/or gracilis tendon. Implant 500 in this exemplary embodiment has aspanning section 516 having a y-shaped or broadened upper end connectingfixation portion 512 and displacement portions 514 and 524 to thefixation portion 512. The displacement of the target tissue can bealtered by changing the thickness, length, curvature and angle of thespanning section and/or displacement portion, or other aspects aspreviously described. The inferior edge of spanning section 516 can alsobe curved to minimize or eliminate any contact with the medial edge ofthe patellar tendon. The superior surface edge of the displacementportion 514 can be contoured to allow for easy motion of the patellartendon during flexion as well as to vary the displacement of thepatellar tendon during flexion. In one exemplary embodiment, theanterior displacement portion 514, extending laterally from the spanningsection 516, is substantially parallel to the tibial plateau. Spanningsection 516 would also be configured to transition from fixation portion512 by curving around the tibia cranially, medially and dorsally tomedial displacement portion 524. Medial displacement portion 524 isconfigured to for positioning between the sartorius or gracilis tendonsand the medial side of the tibia so as to displace these tendonsmedially or antero-medially. The fixation portion could be attached tothe tibia adjacent to the attachment point of the patellar tendon andthe tibia or it could be located more cranial or caudal to theattachment point.

In FIG. 14, fixation portion 532 is used to anchor implant 530 on thetibia and displacement portion 534 displaces the patellar tendon whiledisplacement portion 544 displaces the lateral IT Band. The implant inthis exemplary embodiment has a fixation portion 532 configured forattachment to the tibia medially of the patellar tendon, with a firstspanning section 536 connecting the fixation portion 532 and thepatellar displacement portion 534, and a second spanning section 546connecting the patellar displacement portion 534 and lateraldisplacement portion 544. The displacement of the tissue can be alteredby changing the thickness, length, curvature and angle of the spanningsections and/or displacement portions, or other aspects of the device asdescribed herein. The inferior edge of spanning section 536 can also becurved to minimize or eliminate any contact with the medial edge of thepatellar tendon. The superior surface edge of displacement portion 544can be contoured to allow for easy motion of the patellar tendon duringflexion as well as to vary the displacement of the patellar tendonduring flexion. In one exemplary embodiment, lateral displacementportion 544, extending laterally and dorsally from the spanning section,is substantially parallel to the tibial plateau. Lateral displacementportion 544 is configured for positioning between the IT band and thetibia just cranial to the insertion point of the IT band in the tibia.Spanning section 546 may be configured to transition from the patellardisplacement portion 534 which could be substantially parallel to thetibial plateau to lateral displacement portion 544 configured todisplace the iliotibial band laterally or antero-laterally. In exemplaryembodiments, spanning sections 536, 546 along with displacement portions534, 544 form a generally continuous curve about an axis parallel to thetibial shaft such that the implant conforms to the curvature of theouter surface of the tibia. The fixation portion 532 could be attachedto the tibia adjacent to the attachment point of the patellar tendon andthe tibia or it could be located more cranial or caudal to theattachment point.

In FIG. 15, fixation portion 612 is used to anchor implant 600 onto alateral aspect of the femur, first displacement portion 614 displacesthe quadriceps-femoris tendon and second displacement portion 624displaces the lateral IT Band. Supplementary fixation 618 also may beprovided at the far end of displacement portion 614 and may also includeadditional anchoring features like screw holes, spikes etc. In someembodiments, the implant is anchored only on the lateral side of thefemur, thereby allowing the implantation procedure to be performed by asingle incision. In other embodiments, the opposite side may also beanchored with supplementary fixation 618 using a percutaneous technique,for example, by using a percutaneous screw. Fixation portion 612 isgenerally elongated and configured to be oriented in a directiongenerally parallel to the femoral shaft, with screw holes extendingthrough it in a medial-lateral direction. The displacement of the targettissue can be altered by changing the thickness, length, curvature andangle of the spanning section and/or displacement sections and otheraspects of the device as described herein. First displacement portion614 may be configured to move the tendon anteriorly or medially oranterior-medially or laterally or antero-laterally. This may beaccomplished by making one side (lateral or medial) of the displacementsurface higher than the other, and/or by forming a track with ridges onone or both sides of the bearing surface to urge the tendon in a lateralor medial direction. The inferior region of the displacement portionsmay be contoured to substantially conform to the curved anterior surfaceof the femur. First displacement portion 614 also may be designed to bein contact with the underlying bone or could be elevated so as to avoidcontact with the underlying bone, thereby not disrupting the periosteallayer. The spanning section 616 may have a general y-shape and beconfigured such that first displacement portion 614 is generallyorthogonal the fixation portion 612. One arm of y-shaped spanningsection 616 could extend at an angle medially and anteriorly fromfixation portion 612 to first displacement portion 614. The spanningsection may cantilever or suspend the displacement portion 614 in aposition anteriorly spaced apart from the surface of the femur, toachieve the necessary displacement. This arm of the spanning section mayalso extend more caudally or posteriorly from the fixation portion 612to first displacement portion 614 to avoid any connective tissueattachment points. In some embodiments, the implant may have a secondarm of the y-shaped spanning section 616 that connects the fixationportion 612 to the second displacement portion 624. The second arm mayextend out laterally and caudally such that the displacement portion 624displaces the target tissue laterally over the lateral facet of thefemoral condyle. The second arm also may be configured to positiondisplacement portion 624 under the IT band but laterally spaced apartfrom the surface of the femur to avoid any connective tissue underneaththe displacement section (e.g.; fibular collateral ligament, jointcapsule etc.). The spanning sections may also comprise adjustablemechanisms (e.g. a pin or hinge, hydraulic cylinder, or gear mechanism)to movably or pivotably alter the orientation or angle between the twoparts to achieve the appropriate level of tissue displacement asdescribed herein below. As shown in FIG. 15, the outer surface of seconddisplacement portion 624 has a convex curvature to provide an atraumaticbearing surface for engagement of the IT band. The shape of thedisplacement portion may, in some embodiments, mirror the shape of thelateral aspect of the enlarged lower end of the femur.

In FIG. 16, fixation portion 632 is used to anchor implant 630 onto thefemur, first displacement portion 634 displaces the quadriceps femoristendon and second displacement portion 644 displaces the medialsartorius and/or gracilis tendon. This embodiment of implant 630 isgenerally a mirror-image of implant 600 described above and will sharemany of the same geometrical and other characteristics previouslydescribed, while being adapted for attachment to the medial, rather thanlateral, side of the femur. In some embodiments, the implant is anchoredonly on the medial side of the femur, thereby allowing the implantationprocedure to be performed by a single incision. In other embodiments,the opposite side may also be anchored with supplemental fixation 618using a percutaneous technique, for example, by using a percutaneousscrew. The displacement of the target tissue can be altered by changingthe thickness, length, curvature and angle of the spanning sectionand/or displacement portion and other aspects of the implant asdescribed herein. First displacement portion 634 may be configured tomove the tendon anteriorly or medially or anterior-medially or laterallyor antero-laterally. This may be accomplished by making one side(lateral or medial) of the displacement surface higher than the other,and/or by forming a track with ridges on one or both sides of thehearing surface to urge the tendon in a lateral or medial direction. Theinferior region of the displacement sections may be contoured tosubstantially conform to the curved anterior surface of the femur. Firstdisplacement portion 634 also may be designed to be in contact with theunderlying bone or could be elevated so as to avoid contact with theunderlying bone, thereby not disrupting the periosteal layer. Spanningsection 636 may be configured in a general y-shape such that firstdisplacement portion 634 is generally orthogonal the fixation portion632. The first arm of spanning section 636 may extend at an anglelaterally and anteriorly from fixation portion 632. First arm ofspanning section 636 extends first displacement portion 634 outanteriorly to achieve the necessary displacement. The spanning section636 may also extend more caudally or posteriorly from the fixationportion 632 to the first displacement portion 634 to avoid anyconnective tissue attachment points. In some embodiments, the implantmay have a second arm of spanning section 636 that connects the fixationportion 632 to the second displacement portion 644. The second arm mayextend out medially and caudally such that the displacement portion 644displaces the target tissue medially over the medial facet of thefemoral condyle. The spanning section second arm also may be configuredto hold the displacement portion 644 in a position spaced-apart mediallyfrom the femur to avoid any connective tissue underneath thedisplacement portion (e.g.; tibial collateral ligament, joint capsuleetc.). The spanning sections may also comprise adjustable mechanisms(e.g. a pin or hinge) to movably or pivotably alter the orientation orangle between the two parts to achieve the appropriate level of tissuedisplacement.

FIGS. 17 and 18 show exemplary embodiments of the present invention fordisplacement of the iliotibial band. FIG. 17 schematically depictsimplant 700 anchored on the lateral side of the femur. Fixation portion712 of the implant is used to anchor the implant and displacementportion 714 displaces the iliotibial band. The fixation portion and thedisplacement portion are connected by a spanning section 716 screw orscrews 713 in fixation portion 712 secure the implant.

The embodiments of FIGS. 17 and 18 are particularly effective forreducing the load in the medial compartment of the knee joint. The loadin the medial compartment is the result of the weight of the persondirected caudally through the femur toward the tibia, opposed by anequal and opposite force directed cranially from the ground through thetibia toward the femur. It may be appreciated that the iliotibial (IT)band is attached to the lateral side of the tibial tuberosity at thecranial end of the tibia. The effectiveness of the force exerted by theIT band may be enhanced by increasing the moment arm through which itacts on the joint. Implant 700 displaces the IT band laterally relativeto the joint, thus increasing this moment arm and reducing the load inthe medial compartment.

FIGS. 18A-D depict an exemplary prototype of implant 700 for treatingmedial osteoarthritis for the right knee. Fixation portion 712 isconfigured and dimensioned for attachment of the implant to the lateralside of the distal femur. The implant may be attached with screwspositioned in the screw holes 715. Displacement portion 714, the regionfor displacing the IT band, is connected to fixation portion 712 throughspanning section 716. The displacement of the tissue can be altered bychanging the length, shape, and angle of the spanning section 716, theshape, thickness and orientation of displacement portion 714, and otheraspects of the implant as described herein.

In this exemplary embodiment, fixation portion 712 comprises a generallyelongated section of the implant configured to be oriented along thelongitudinal axis of the femoral shaft. An inner surface of fixationportion 712 has a concave curvature about its longitudinal axisgenerally matching that of the outer surface of the femur to maximizesurface contact between fixation portion 712 and the underlying bone.Screw holes 715 extend through fixation portion 712 such that screws maybe inserted through them in a medial direction into the femur.Displacement portion 714 is preferably separated or offset horizontally(i.e. cranially, caudally, laterally or medially) from fixation portion712. In the embodiment illustrated, spanning section 716 extendslaterally and caudally from fixation portion 712 to displacement portion714. Displacement portion 714 is attached along its proximal edge tospanning section 716, with its opposing distal edge being a free end. Inthis way implant 700 may be fixed to the bone only at its proximal endwhere fixation portion 712 is located, while remaining unattached to thebone at its free distal end where displacement portion 714 is located.Of course, in some embodiments implant 700 may have one or moreadditional fixation portions, e.g. attached to the distal, ventral, ordorsal edges of displacement portion 714, such that implant 700 may besecured to the bone at both ends or along its edges.

Displacement portion 714 preferably has an enlarged spoon-like roundedshape similar to the lateral profile of the lower end of the femur. Inpreferred embodiments, fixation portion 712 has a length L_(A) (FIG.18B) selected to extend longitudinally along the femur sufficiently tostabilize the implant and to accommodate the desired number of hole(s)to receive screws for anchoring to the femur. In preferred embodimentslength L_(A) may be 25-65 mm, more preferably 30-60 mm, and mostpreferably 35-55. The combined length L_(A) of the spanning section 716and displacement portion 714 will be selected to position thedisplacement portion under the IT band laterally of the distal end ofthe femur, with the distal (caudal) end 721 of displacement portion 714being at the level of the gap between in the femur and the tibia.Displacement portion 714 preferably has a convex curvature on its outeror lateral side, and a concave curvature on its inner side. Displacementportion 714 has an outer bearing surface 730 which engages the IT band.The bearing surface 730 is smooth, rounded and low-friction to minimizewear and trauma to the IT band. In preferred embodiments, bearingsurface 730 is free of significant ridges, bumps, voids, holes or otherdiscontinuities of the kind that would cause abrasion or wear of thetarget tissue, particularly larger holes or channels for fixationdevices such as screws or K-wires. Bearing surface 730 may comprisesimply a smoothed and/or polished region of displacement portion 714, orit may comprise a coating or layer of a different material, e.g. alubricous biocompatible polymer. In other embodiments, bearing surface730 may have holes, protuberances, a polymeric or drug coating, or otherfeatures to promote adhesion with the displaced target tissue such thatmovement between the target tissue and implant 700 is minimized.

Preferably the inner and outer surfaces have curvature about multipleaxes, and may be generally or partially spherical. The radius ofcurvature R_(A) of the outer surface, shown in FIG. 18C, is selected toprovide the optimal displacement of the IT band throughout the range ofmotion of the knee. In some embodiments the shape and curvature of theouter surface will be selected such that the IT band is under asubstantially constant magnitude of displacement throughout the range ofknee motion, while in other embodiments, the shape and curvature of theouter surface will be selected to displace the tissue more in certainportions of the range of motion, while reducing the displacement inother regions of the range of motion. Curvature R_(A) of the outersurface of displacement portion 714 is usually about 15-35 mm, morepreferably 20-30 mm, and most preferably 23-27 mm.

Displacement portion 714 may be cantilevered or suspended by spanningsection 716 in a plane laterally displaced from or angled relative tofixation portion 712 such that it is spaced apart from the lateralsurface of the femur when the implant is fixed in its implantedposition. This provides space between the femur and the displacementportion through which non-target soft tissues may reside and/or movewithout interference. In a preferred embodiment, spanning section 716extends laterally and caudally at an oblique angle relative to fixationportion 712 such that a plane P tangent to the surface of the spanningsegment 716 is disposed at an angle θ relative to a centerline C throughfixation portion 712 of between 30-60° more preferably 35-55°, and mostpreferably 42-48°.

Spanning section 716 may be substantially rigid such that displacementportion 714 remains stationary relative to the femur under the loadsexerted by the IT band. Alternatively, spanning section 716 and/ordisplacement portion 714 may have some degree of flexibility so as toallow some movement of displacement portion 714 relative to the femurunder certain loads. For example, spanning section 716 may have aflexibility selected such that if loads on displacement portion 714exceed a preselected threshold, spanning section 716 will flex to allowdisplacement portion 714 to be deflected relative to the femur.

The anterior edge 705 of the implant is preferably curved (Radius ofcurvature R_(B) in FIG. 18B) to avoid contact with the lateral edge ofthe patella. The posterior edge 706 of the implant is also preferablycurved (Radius of curvature R_(c) in FIG. 18B) to avoid contact with thefibular head during knee flexion. In some embodiments, the distal,anterior and posterior edges of the displacement section 714 are shapedto form an arc (Radii of curvature R_(B), R_(c) and R_(D) in FIG. 18B)similar to the lateral profile of the distal end of the femur viewed inthe sagittal plane.

In some embodiments, the distal, anterior and posterior edges of thedisplacement section 714 are shaped to form an arc (Radii of curvatureR_(x), R_(y) and R_(z) in FIG. 18D) viewed in the transverse plane. Theanterior edge 705 may also be shaped to minimize displacement(anteriorly or laterally) of the lateral edge of the quadriceps-femoristendon/muscle. Alternatively, anterior edge 705 may be shaped to extendunder the quadriceps-femoris tendon to anterioralize or lateralize thelateral edge of the quadriceps-femoris tendon/muscle. The posterior edge706 may be shaped to minimize displacing the IT Band during highflexion. The posterior edge may also be extended posteriorly such thatthe anterior edge of the IT Band remains on the implant surface duringhigh flexion. The inside surface 721 of the displacement portion 714 ispreferably concave with a spoon-like shape to minimize contact withunderlying soft tissue including lateral ligaments, the joint capsule,etc. In one exemplary embodiment as shown, the fixation portion 712 istapered from the distal (or caudal) end to the proximal (or cranial)end. In other embodiments, the fixation portion 712 may have constantwidth. In the exemplary embodiment as shown, the width of thedisplacement portion 714 is substantially larger than the width offixation portion 712, contributing to the overall spoon-like orpaddle-like shape of implant 700. Displacement portion 714 is once againjoined to fixation portion 712 by a spanning section 716.

The curvature of the displacement portion 714 may be configured todisplace the target tissue, e.g. the iliotibial band, laterally orantero-laterally. In some embodiments, the anterior region of thedisplacement portion 714 may extend out more laterally than theposterior region of the displacement section. In one exemplaryembodiment, the implant is placed on the lateral side of the distalfemur such that fixation portion 712 is substantially aligned with thefemoral shaft, the spanning section 716 is in close apposition to theregion of the femur where the femoral shaft joins the femoral condyle,and the displacing portion 714 substantially covers or lies generallyparallel to the lateral facet of the femoral condyle. In someembodiments, the top view of the implant would mirror the lateral viewof the distal femur, wherein the implant has shaft region similar to thefemoral shaft, an expanding neck region similar to the condylar flareand a circular or oval or elliptical region similar to the condyle.Typical dimensions of embodiments of implant 700 (FIGS. 18A-D) would beas follows: L_(A) about 40 to 55 mm, L_(B) about 45 to 60 mm, T₂ about2.5 to 5.0 mm, R_(A) about 23 to 27 mm, R_(B) about 12 to 18 mm, R_(C)about 12 to 18 mm, R_(C) about 25 to 33 mm, θ about 40 to 50°, W₁ about12 to 18 mm, W₂ about 45 to 60 mm, D about 10 to 45 mm, R_(X) about 35to 40 mm, R_(Y) about 20 to 25 mm, R_(Z) about 27 to 33 mm, X about 40to 50°, Y about 20 to 30° and Z about 25 to 35°. In exemplaryembodiments, the size of the implant (as seen in the top view) would beproportionally smaller than the lateral profile of the femoral condyle,preferably 1-40% smaller, more preferably 5-25% smaller, and mostpreferably 10-20% smaller.

EXAMPLE

An exemplary embodiment of the present invention as shown in FIGS. 18A-Dwas subjected to simulated load testing. Dimensions of the implanttested were: W₁=23 mm, W₂=50 mm, L_(A)=35 mm, L_(B)=40 mm, D=30 mm. Thetest was conducted as follows: Using a robotic testing system forevaluating knee joint biomechanics, as described by Gadikota et al.,American Journal of Sports Medicine, 38, 713-720, 2010, simulations wererun using cadaveric human knee specimens. Eight fresh-frozen cadaverichuman knee specimens (4 male, 4 female, Age: 36-50 y) stored at −20° C.were thawed at room temperature prior to testing. The quadriceps muscleswere loaded at 300 N, the hamstrings at 100 N, and the iliotibial bandat 0, 50, and 100 N to simulate a variety of loading conditions. Thedisplacement of the IT Band ranged from 15 to 20 mm. The robotic testingsystem was used to determine knee joint kinematics and contact forces inthe medial and lateral compartments from 0° to 30° flexion, with andwithout the exemplary implant (FIG. 18).

Results:

-   -   Average medial compartment load measured from 0° to 30° flexion        for the eight specimens was reduced by about 56% at IT Band        loading=0 N, about 43% at IT Band loading=50 N, and about 49% at        IT Band loading=100 N.    -   Average valgus/varus orientation of the knee measured from 0° to        30° flexion for the eight specimens was more valgus by about        0.4° at IT Band loading=0 N, about 0.3° at IT Band loading=50 N,        and about 0.3° at IT Band loading=100 N.    -   Average internal/external rotation of the knee measured from 0°        to 30° flexion for the eight specimens was more externally        rotated by about 0.4° at IT Band loading=0 N, substantially        unchanged at IT Band loading=50 N and more internally rotated by        about 0.2° with the IT Band=100 N.        These results show that lateral displacement of the IT Band in        the range disclosed in the present invention results in decrease        in articular cartilage loading in the target knee compartment        (medial). The experimental results further show that displacing        the IT Band with a prosthesis described in the present invention        alters the kinematics of the target joint.

FIGS. 19 and 20 depict portions of further exemplary implants accordingto the present invention and optional features thereof. In onealternative, the fixation portion comprises a base plate 812 that can beattached to the underlying bone with screws through holes such as holes815. Upper plate 814 comprises the displacement portion and may beattached to target tissue with sutures, adhesives, tissue in-growth etc.For example, in FIG. 19, holes 822 are provided for suturing.Alternatively, the upper plate may have surface features like increasedroughness, beads etc. as previously describe that minimize slippagebetween the connective tissue that lies over the plate and the plateitself. The plates may be fabricated from metal or polymeric substrate.A capsule 816, acting as a spanning section, joins upper plate to baseplate and allows relative motion between plates. There is little or norelative motion between the displaced soft tissue and implant surfaceand no relative motion between the bone and the implant surface. Withlittle or no motion between the soft tissue and top plate, wear concernsare minimized. In some embodiments, motion may be along all three axesas well as rotational. The sealed capsule may be fabricated from aninelastic material or a stretchable or deformable material (such assilicone, polyurethane etc.) which is attached to the plates. Thecapsule may be filled with gel, saline, balls, beads etc. Alternatively,a capsule may enclose the entire construct, thereby eliminating anycontact between the plates and the surrounding tissue. A sealed capsulewould isolate the moving surfaces from biological interference (scartissue, fibrotic coverings, encapsulation, clotting etc.).

In a further alternative, material may be added to or removed fromcapsule 816 to adjust the distance between the plates. As shown in anexemplary embodiment in FIG. 21, capsule 816 may have separate chambersto selectively alter the displacement of the plates. Each chamber 816a-c preferably has its own injection port or valve (not shown) throughwhich a liquid or gaseous filler material may be introduced. Chambers816 a-c may have different volumes, and may be filled with different oridentical fillers. The volume of material in each chamber may be changedpost-implant as needed to optimize treatment. For example, if the softtissue being displaced stretches or moves over time, material may beadded or removed from each chamber to maintain the desired degree anddirection of displacement.

In other embodiments, the capsule 816 may be replaced by an elastomericor sponge like material which can be assembled in multiple layers tovary the displacement between the plates. Alternatively one or moresprings may interconnect the two plates.

Exemplary device shown in FIGS. 19 and 20 may also be used fordiagnostic purposes. The device may be implanted in humans, cadaverictissues or in animal models, and the plates could be visualized viafluoroscopy or other imaging techniques. Visualization of the platesduring flexion/extension or other joint motion would help understand thecomplex relationship between the soft tissue and underlying bone duringjoint motion, thereby enabling design of implants with bettertherapeutic or safety features.

FIG. 22 depicts a portion of a further alternative exemplary implant ofthe present invention with features in common with the implants shown inFIGS. 19 and 20. In this embodiment base plate 812 is attached to theunderlying bone with screws etc. and the upper plate 814 is attached tosoft tissue as previously described. Again, the plates may be fabricatedfrom metal or polymeric substrate. The upper plate and lower plates aresupported by a mechanical coupling 825 that allows motion there between.Coupling 825 allows motion in multiple directions and could also beadjusted to alter the distance between the two plates. The mechanicalcoupling may be encased in a capsule to isolate the mechanism from scartissue formation etc. There would be motion between the top plate andthe base implant, but little or no motion between the soft tissue andtop plate, thereby minimizing wear concerns. The mechanical coupling maybe fabricated from metal or polymeric substrates. In some embodiments,motion may be provided for along all three axes as well as rotational.In other embodiments, the bottom plate may comprise a further spanningsection and a fixation section such that the displacement section is notin contact with bone. For example, the exemplary embodiments shown inFIGS. 19, 20, 21 and 22 could be configured to be attached to or mountedon the displacement region 214 (FIG. 7), 314 (FIG. 9), 414 (FIG. 10),424 (FIG. 11), 434 (FIG. 12), 614 (FIG. 15), 624 (FIG. 15), 634 (FIG.16), 644 (FIG. 16), 714 (FIG. 17) etc. The device may also be used fordiagnostic purposes as described above.

One exemplary implant employing features as shown in FIGS. 19-21 isshown in FIG. 23. In this embodiment implant 830 includes a displacementportion 814 which is in contact with the IT Band. Base plate 812comprises the fixation portion and is secured to the bone via screws813. Capsule 816 forms a moveable spanning section between the twoplates, allowing the plates to move relative to one another. Thispermits relative motions between the IT band and the femur whileavoiding friction or wear due to movement of the IT band over theimplant.

Another exemplary embodiment with a capsule is shown in FIG. 24.Fixation portion 852 of implant 850 is configured to be attached tobone. This embodiment may have a configuration adapted for attachment tothe lateral femur and displacement of the IT band like that describedabove in connection with FIGS. 18A-C, and may have a similar geometry.Displacement portion 854 may be in contact with the underlying bone orsoft tissue like ligaments etc. or it may be spaced apart from theunderlying tissue (to provide space for e.g.; collateral ligaments,joint capsule etc.). In this embodiment, a separate bearing member 857forms the top plate as previously described with a capsule 855interposed between the bearing member and bottom plate of thedisplacement portion. The spanning section 856 may be configured toalter the position of the displacement portion 854 relative to thefixation potion 852. The displacement portion 854 may lie generally in aplane parallel to that in which the fixation portion 852 lies, and thespanning section 856 may extend at an angle or be curved laterally andcaudally from fixation portion. In other embodiments, the implant may beanchored on the medial side of the femur and the spanning section mayextend at an angle medially and caudally from the fixation portion.

FIG. 25 depicts a further alternative exemplary implant 860 according tothe present invention. Fixation portion 862 is configured to be attachedto bone. Displacement portion 864 includes a sealed capsule 865,attached to a side opposite the bone. The sealed capsule could befabricated with an inelastic or stretchable or deformable material (suchas silicone, polyurethane etc.). The capsule will preferably have aninlet port or valve (not shown) through which it may be filled with air,gas, water, gel, saline, metal or polymer balls, beads etc. Solidifyingmaterials such as two-part epoxies may also be used as fillers. Thecapsule 865 could be inflated to an expanded shape (indicated by dashedlines 865 a) by addition of the filler as required to achieve thenecessary tissue displacement. Displacement portion 864 may be incontact with the underlying bone or soft tissue like ligaments etc. orit may be displaced from the underlying tissue (for e.g.; collateralligaments, joint capsule etc.). The spanning section 866 may beconfigured to alter the position of the displacement portion 864relative to the fixation portion 862. The displacement portion 864 maylie in a plane generally parallel with a plane containing the fixationportion 862, and the spanning section 866 may extend at an angle or becurved laterally and caudally from fixation portion. In otherembodiments, the implant may be anchored on the medial side of the femurand the spanning section may extend at an angle medially and caudallyfrom the fixation portion.

FIG. 26 depicts another alternative exemplary implant 800 according tothe present invention. Fixation portion 882 of implant 880 is configuredto be attached to bone. Displacement portion 884 has a capsule 885,attached to an inner surface of the implant, facing the bone. Thefixation portion and displacement portion are movably or pivotablyinterconnected with an adjustable attachment 889, e.g. a pin or hinge.The orientation or angle between the two parts can be altered to achievethe appropriate level of tissue displacement. The capsule 885 will havean inlet port or valve (not shown) through which it may be filled withair, gas, water, gel, saline, balls, beads etc. The capsule 885 could beinflated to an expanded state (indicated by dashed line 885 a) byaddition of material as required to achieve the necessary tissuedisplacement. The adjustable attachment 889 could be locked in the finalposition once the soft tissue has been displaced appropriately.Alternatively, the adjustable attachment may include a one-way mechanismlike a ratchet mechanism.

In some embodiments, the capsule, for example capsules 865 or 885, mayhave multiple chambers that could be inflated independently. The surfaceof the capsule could be modified as needed for interaction with thesoft/hard tissue. For example, the surface could be smooth to allow foreasy movement of the soft tissue across the surface. Alternatively, thesurface may have an adhesive surface to allow attachment to underlyingbone or soft tissue. The surface could be coated with a hydrophilic orhydrophobic layer. The surface may have a polymeric coating for drugrelease. Drugs like anti-inflammatory drugs and antibiotics could beincorporated into the polymeric coating. The capsule may be filled witha liquid or gas under suitable pressure to allow adjustment of thebearing member position and associated displacement of the targettissue. The bladder will have an inflation port for introduction ofinflation fluid by means of an inflation device, which may be similar tothe inflation devices used for inflation of angioplasty balloons as willbe understood by persons of ordinary skill in the art.

In some embodiments of the present invention, the displacement of theconnective tissue could be adjusted by adjusting the devicepre-operatively, intra-operatively or post-operatively. Devices mayinclude mechanisms that are remotely controlled and/or enable wirelesscommunication to alter the displacement after implantation.Alternatively, the displacement may be adjusted by applying an energyfields (e.g.; magnetic field, electric field, thermal field etc.)transdermally from an external location.

In various adjustable embodiments described above, the adjustmentmechanisms themselves may be radiopaque and/or otherwise discernablefrom the rest of the implant under x-ray in order to enablepost-surgical percutaneous adjustment of the device. Alternatively,target features can be built into the device to locate the adjustmentpoints without having the screws or adjustment means themselvesradiopaque, such as radiopaque rings or markers built into the nearingsurface of the device itself.

The implants described above may be implanted in areas adjacent to thejoint such that the soft tissue is displaced in a region it crosses thejoint. Alternatively, the device could be implanted away from the jointand displace the target soft tissue in a region that it is not crossingthe joint. For example, the device could be implanted distally on thelateral femur close to the lateral femoral condyle to displace the ITBand as it crosses the joint or the device could be implanted moreproximally along the femoral shaft where it displaces the IT Band in aregion away from the joint (FIG. 23). Similarly, the device could beimplant further up along the femoral shaft where it displaces thesartorius and gracilis muscle in a region away from the joint.

Embodiments of the present invention may also be configured to displacetissue by pulling the tissue away from the joint to increase the momentarm, rather than pushing it away as in some other embodiments. Oneexemplary embodiment of such a device is shown in FIG. 27. In thisembodiment, apparatus 900 comprises fixation portion 912, herecomprising separate anchors 912A, 912B configured for mounting to thelateral aspect of the tibia T. Each anchor member 912A, 912B has aplurality of holes 915 to accommodate anchoring screws 913. A generallyrigid pivoting arm 904 is pivotably coupled to first anchor 912A so asto be movable rotationally about pivot point 906. The cranial end ofpivoting arm 904 is pivotably mounted to a tissue hook 908 which isconfigured to at least partially encircle iliotibial band ITB. Anadjustment arm 910 is pivotably mounted to second anchor 912B on itscaudal end and to tissue hook 908 on its cranial end. Adjustment arm 910has an axial length adjuster 922 coupled thereto, which in an exemplaryembodiment may comprise a threaded tube into which two opposing segmentsof adjustment arm 910 are threaded with opposite handed threads. In thisway the length of adjustment arm 910 may be shortened or lengthened. Itmay be seen that as adjustment arm 910 is shortened it pulls on tissuehook 908, which pivots laterally on pivoting arm 904. This displacesiliotibial band ITB laterally, away from the center of the knee, thuslengthening the moment arm of the force exerted on the joint byiliotibial ITB and moving the resultant force vector in the lateraldirection, reducing the force in the medial compartment of the joint. Inthis embodiment tissue hook 908 forms a displacement portion andadjustment arms 910 a spanning section.

It will be appreciated that anchors 912A-B may have a shape selected toallow secure anchoring to the bone and to avoid soft tissues and bonyfeatures on the tibia. In addition the various components of apparatus900 will be configured to minimize engagement with and abrasion of thesoft tissues surrounding the joint, without sharp edges or catch points.Apparatus 900 may optionally be covered or coated with a soft orfriction-reducing material.

The apparatus of FIG. 27 may alternatively be configured for attachmentto the medial side of the tibia to displace the Sartorius muscle ortendon, the Gracilis muscle or tendon, or other suitable tissues for thetreatment of lateral osteoarthritis. Moreover, apparatus 900 may beconfigured for mounting to the fibula FIB instead of or in addition tothe tibia. Further, apparatus 900 may be configured for mounting to thefemur F in an upside down orientation relative to that depicted in FIG.17.

In another alternative embodiment shown in FIG. 28, implant 1000 mayinclude a displacement portion 1014 with a roller or rollers embedded init or mounted on it to ease the motion of the patellar tendon across theimplant surface during flexion/extension and reduce any wear due to themotion of tissue across the implant surface. In one embodiment, roller1022 is embedded in displacement portion 1014 of the implant. The axisof rotation of the roller could be essentially parallel to the tibialplateau axis such that the axis of motion of the patellar tendon isessentially orthogonal to the axis of rotation of the roller. The rollercan rotate freely in both directions (clockwise and counter clock-wise).The position or thickness of the displacement portion 1014 and thediameter of the roller 1022 can be adjusted to obtain the necessaryamount of anterior displacement of the patellar tendon. Displacementportion 1014 may otherwise cooperate with a fixation portion and aspanning section as previously described.

In other alternative embodiments, displacement portions of previouslydescribed static implants may be provided with a roller or other dynamicfeature to further reduce wear or trauma to the displaced tissue. Forexample, displacement portions 414, 424 or 434 of implants 400, 420 and430, respectively, may have a roller or rollers 1022 mounted thereon toease the motion of the quadriceps tendon across the implant surfaceduring flexion/extension and reduce any wear due to the motion of tissueacross the implant surface as shown in FIG. 29. The roller 1022 isembedded in the displacement portion of the implant. The axis ofrotation of the roller could be essentially parallel to the femoralcondyle axis (medial-lateral) such that the axis of motion of the tendonis essentially orthogonal to the axis of rotation of the roller. Theroller can rotate freely in both directions (clockwise and counterclock-wise). The thickness of displacement portion and the diameter ofthe roller can be adjusted along with other aspects of the device aspreviously described to obtain the necessary amount of anteriordisplacement of the quadriceps femoris tendon.

FIG. 30 depicts an alternative exemplary two piece implant 1100according to an embodiment of the present invention for treating medialosteoarthritis wherein the two pieces are independent of each other andarticulate over each other during joint motion. Fixation portion 1112 ofimplant 1100 is the fixed section of the implant and is attached to thebone with screw or screws 1113. Displacement portion 1114 includes amobile bearing member 1117 that bears upon fixed surface 1120 ofdisplacement portion 1114. With this configuration, mobile bearingmember 1117 may be attached to the target soft tissue T. Either fixationportion 1112 or displacement portion 1114, or both may have a shape andsize selected to displace mobile bearing 1117, and thus tissue T, thedesired degree. The two piece design enables articulation between thesurfaces of displacement portion 1114 and mobile bearing 1117; andreduces the risk of tissue wear due to motion of soft tissue over theimplant surface. Mobile bearing member 1117 may be attached to the softtissue using sutures, adhesives, pins etc. or otherwise as describedabove, including having the surface in contact with the soft tissuemodified to enable tissue integration. The articulating surfaces betweenparts 1114 and 1117 also may have features like grooves to enable onesurface to track a fixed path during flexion. The surfaces could becoated to minimize friction and wear. In some embodiments, the mobilesection is attached to or embedded in the IT Band. In other embodiments,the mobile section may be attached or embedded into the patellar tendon,the quadriceps femoris tendon, or any other soft tissue surrounding thetarget joint. In some embodiments, bearing member 1117 may comprise of asoft, flexible, polymer membrane which can conform to the soft tissueand prevent contact between the soft tissue and the implant surface1120. In other embodiments, bearing member 1117 may be inflatable, orinclude a capsule as previously described.

In further alternative embodiments, implants may also be fabricatedin-situ by layering a polymerizing material on the underlying tissuesuch as in the embodiments of FIGS. 31 and 32. In such an embodiment, animplant could be contoured as needed by varying the material beinglayered in different regions of the implant. Removable molds or formsmay be placed through an incision to the desired location against thebone to facilitate containment and shaping of the material prior tosolidifying. In one exemplary shown in FIG. 31, implant 1200 includeslayers 1201, 1202 and 1203, layered on top of each other to achieve thenecessary displacement. The materials and the properties of each of thelayers could be identical or different. For example, layer 1201 may haveadhesive properties to attach to the underlying bone, layer 1202 mayhave high compressive strength to withstand the compressive load of theoverlying soft tissue and layer 1203 may have a smooth hydrophilicsurface to minimize friction between the implant and the soft tissueduring flexion/extension. In this example, layer 1201 provides thefixation portion and layer 1203 the displacement portion with layer 1202forming a spanning section there between. Adhesives may be used betweenthe various layers. The materials could be polymerized in-situ usingchemical crosslinkers, photo-initiated crosslinkers, thermally initiatedcrosslinkers, etc. The thicknesses of the various layers could bealtered to achieve the necessary level of tissue displacement.

In an alternative exemplary embodiment of an in situ fabricated implant,as shown in FIG. 32, a spacer 1210 may be used to assist in fabricatingthe implant. The spacer 1210 could potentially be removed after theimplant has been fabricated, leaving behind a gap (G) between section1201 and the underlying soft tissue and bone. However, the implant maybe designed to rest permanently on the underlying soft tissue and bone.

In yet another exemplary embodiment of the present invention, thedisplacement of the connective tissue may occur at a region away fromthe joint. For example, as depicted in the exemplary embodiment of FIG.23, the iliotibial Band is displaced laterally substantially proximallyalong the femoral shaft with an exemplary device. Similarly, the in-situfabricated implant could be located such that it displaces the targetsoft tissue around the target joint or at a site away from the targetjoint.

A further aspect of the present invention includes methods for treatingknee joints and implanting prostheses as described herein. One exemplarymethod thus comprises selecting at least one of the associated muscleand connective tissues surrounding a joint as target tissue fortreatment, displacing the target tissue without severing the bones ortarget tissue, and altering the kinematics of the joint. In a furtherembodiment, altering the kinematics of the joint achieves a therapeuticeffect. In other embodiments, altering the kinematics of the jointredistributes loading in the joint, and or reduces loading on theligaments within the joint. In some embodiments prostheses according tothe present invention may be placed with therapeutic effect withoutrupturing the joint capsule.

In some embodiments, the inferior surface of the displacement region iselevated off the underlying tissue. The underlying tissue could be boneor soft tissue like tendon, muscle, ligament, bursa, capsule etc. FIG.33 depicts an implant 1500 with the inferior surface 1504 of thedisplacement section 1502 elevated off the underlying tissue. Elevatingthe inferior surface off the underlying tissue could be beneficial byminimizing interference with or damage to soft tissue, reducing anypotential restriction to joint motion due to compression of soft tissueetc.

Elevation of the IT band above the underlying tissue (bone, bursa etc.)by the prostheses disclosed in the present invention may also beeffective in alleviating IT band pain.

In some embodiments, the displacement region will have a continuousbearing surface which is in contact with the target connective tissue(muscle, tendon, ligament etc.) and is devoid of any discontinuities.Such discontinuities are usually undesirable as they create voids andinterruptions in the smooth bearing surface, may have sharp edges ortransitions, and may cause wear or abrasion of the displaced targettissue. Discontinuities would include fixation channels for long-termfixation like screw holes, holes for sutures etc. as well as fixationchannels for temporary fixation like holes for Kirschner-wires(K-wires).

FIG. 33 depicts an implant 1500 with a displacement section 1502 with asuperior bearing surface 1503 and an inferior surface 1504. Displacementsection 1502 is free of discontinuities in the bearing surface, such asholes that extend from the superior bearing surface 1503 to the inferiorsurface 1504 or those that extend from the superior bearing surface 1503part way to the inferior surface 1504. The lack of discontinuities inthe bearing surface minimizes the potential for wear or irritation ofthe target connective tissue. The bearing surface of the displacementsection may be polished, coated, covered, or modified in other ways tominimize wear of the bearing surface and/or wear of the targetconnective tissue.

In some embodiments, the bearing surface of the displacement regionwhich is in contact with the target connective tissue (muscle, tendon,ligament etc.) may have features that enable adhesion or attachment ofthe target connective tissue to the bearing surface. Attachment of thetarget connective tissue on the implant surface may minimize motion ofthe tissue across the implant surface during joint motion. Thesefeatures would include channels for formation of fibrous tissue from thetarget connective tissue anchoring the connective tissue to thedisplacement surface of the implant.

FIG. 34 depicts an implant 1510 with channels 1515 that extend from thesuperior bearing surface 1513 to the inferior surface 1514. FIG. 35depicts an implant 1520 with channels 1525 extend from the superiorbearing surface 1523 part way to the inferior surface 1524. The channels1515 and 1525 may have varying cross-sectional shapes, for example;square, circle, rectangle, oval etc., with the largest cross-sectionaldimension (for example, diameter of the circle, diagonal of a square orrectangle, major diameter of an oval etc.) and will be dimensioned topromote adhesion and ingrowth of the target tissue, usually ranging fromless than 1 mm to about 5 mm. The channels may be located across theentire bearing surface or across part of the bearing surface. In someembodiments, the displacement region may have one channel. In someembodiments, the displacement region may have two channels. In someembodiments, the displacement region may have three channels. In someembodiments, the displacement region may have more than three channels.In some embodiments, the channels may vary in depth across the bearingsurface. The dimensions and cross-sectional shape of the channels acrossthe displacement region may be identical or different. In someembodiments, the spanning section (e.g., 1516 and 1526) and/or thefixation section (e.g., 1511 and 1521) may also have similar featuresfor attachment of the target connective tissue. In some embodiments, aregion of the displacement section may have features for attachment oftarget connective tissue.

In some embodiments, the bearing surface of the displacement region mayhave surface features that enable adhesion or attachment of the targetconnective tissue to all or part of the bearing surface. These featureswould include projections, microprojections, bumps, ridges, pin-likeprojections, a granular surface, a sintered layer, etc.

FIG. 36 depicts an implant 1530 with projections 1535 on the superiorsurface 1533 of the displacement section 1532. FIG. 37 depicts animplant 1540 with ridges on the superior surface 1543 of thedisplacement section 1542. FIG. 38 depicts an implant 1550 with a porousor granular surface 1555 on the superior surface 1554 of thedisplacement section 1552. In some embodiments, the spanning section(e.g., 1556) and/or the fixation section (e.g., 1551) may also havesimilar features for attachment of the target connective tissue. In someembodiments, a region of the displacement section may have features forattachment of target connective tissue.

In some embodiments, the inferior surface of the displacement region maybe in contact with the underlying tissue. FIG. 39 depicts an implant1560 with the inferior surface 1564 of the displacement section 1562 incontact with the underlying tissue. In other embodiments, part of theinferior surface of the displacement section may be in contact with theunderlying tissue.

In some embodiments, the inferior region of the displacement portion,spanning portion, or fixation portion may have features like channelsfor fibrous or bony tissue ingrowth to enable adhesion or attachment ofthe underlying tissue to the bearing surface. In other embodiments, theinferior region may have features like projections, microprojections,bumps, ridges, pin-like projections, granular surface etc. Attachment ofany soft connective tissue underneath the inferior surface of thedisplacement region may minimize motion of the tissue under the implantduring joint motion. In other embodiments, the inferior surface may havepins for anchoring the implanting into underlying bone.

FIG. 40 depicts an implant 1570 with channels 1575 in the inferiorportion 1574 of the displacement section 1572. The channels 1575 mayhave varying cross-sectional shapes, for example; square, circle,rectangle, oval etc., with the largest cross-sectional dimension (forexample, diameter of the circle, diagonal of a square or rectangle,major diameter of an oval etc.) ranging from less than 1 mm to about 5mm. The channels may be located across the entire inferior surface oracross part of the inferior surface of the displacement section.

FIG. 41 depicts an implant 1580 with projections 1585 from the inferiorsurface 1533 of the displacement section 1582. FIG. 42 depicts animplant 1590 with pins 1595 and 1596 from the inferior surface of thedisplacement section 1592.

In some embodiments, the device may be a two-part device with the firstpart (base unit) comprising the fixation section, the displacementsection (and optionally, the spanning section), and the second part(bearing unit) configured to attach to the displacement section of thebase unit. In other embodiments the bearing unit may be configured toattach to the spanning section and to cover the displacement section ofthe base unit. The bearing unit may be configured to minimize tissuewear or to enable tissue adhesion or attachment. In one embodiment, thedisplacement section and the bearing unit would have features to attachthe two units.

FIG. 43 depicts an exemplary two-part implant with a base unit 1600 anda bearing unit 2600. FIG. 47 depicts another exemplary embodiment of atwo part implant with a bearing unit 2800 slipped over the displacementsection of the base unit 1800. Attachment of the bearing unit wouldincrease the depth of the composite implant D (FIGS. 43, 45, & 47). Toalter the depth of the composite implant, bearing units of differentdimensions D₁ and D₂ (FIG. 44) may be attached intra-operatively to abase unit before it is anchored to the target site or to a base unitthat has been anchored to the target site (e.g., femur, tibia etc.) toobtain the necessary target connective tissue displacement. In someembodiments, the bearing unit may cover the entire displacement sectionof the base unit. In other embodiments, the bearing unit may cover partof the displacement region. In some embodiments, the bearing unit 2700may extend beyond the displacement section of the base unit 2700 (FIG.45). The bearing unit may be rigid, or may comprise of a rigid base 3000with a compliant surface 3100 (FIG. 46).

In some embodiments, the displacement region may have channels to assistin positioning, placement or temporarily anchoring of the implantintra-operatively. FIG. 48 depicts an implant with channels 1901 in thedisplacement section 1902 to assist in positioning of the implant duringa percutaneous or minimally invasive surgery. FIG. 49 depicts an implantwith channels 1911 and 1912 in the displacement section 1902 to assistin positioning of the implant during a percutaneous or minimallyinvasive surgery. The channels may be covered with caps (e.g., 2001,2012, 2011) configured to fit into the channels to render the bearingsurface of the displacement region completely smooth and substantiallydevoid of any discontinuities.

While FIGS. 33-49 illustrate exemplary embodiments of the presentinvention in relationship to the distal femur, it will be evident to oneskilled in the art that the invention may further be adapted to variousother joint locations.

FIGS. 50A-E and 51 depict another exemplary prototype of implant 5000for treating medial osteoarthritis for the right knee. Implant 5000 mayhave any of the attributes, shapes, dimensions, materials, or otherfeatures of the embodiment of FIGS. 18A-D, with the possible additionsor variations described hereinbelow. Fixation portion 5012 is configuredand dimensioned for attachment of the implant to the lateral side of thedistal femur. The implant may be attached with screws positioned in thescrew holes 5015. Displacement portion 5014, the region for displacingthe IT band, is connected to fixation portion 5012 through spanningsection 5016. The displacement of the tissue can be altered by changingthe length, shape, and angle of the spanning section 5016, the shape,thickness and orientation of displacement portion 5014, and otheraspects of the implant as described herein.

While the overall size of implant 5000 is preferably minimized,displacement region 5014 should be large enough such that the IT banddoes not slip off its surface at any point along its trajectory ofmotion from full knee flexion to full extension. In addition, the shape,size, and curvature of the displacement region 5014 are selected suchthat the IT band, at any point along its range of motion, is engaged ina direction perpendicular to a tangent to the surface of thedisplacement region and is not engaged by one of the edges of theimplant. It may be seen in the lateral elevational view of FIG. 50B thatimplant 5000 preferably has a shape which is asymmetrical about alongitudinal axis L drawn in the cranial-caudal direction through themidline of the implant. The posterior edge 5006 extends further awayfrom axis L than the anterior edge 5005 such that the posterior portion5020 of displacement region 5014 has a larger area than the anteriorportion 5022. This larger extension in the posterior direction ensuresthat the IT band is engaged by the implant throughout its full range ofmotion and does not slip off the surface of the displacement region 5014on the posterior side when the knee is fully flexed. At the same time,the posterior edge 5006 is tailored to avoid contact with tissue on thefemoral condyle or the tibia throughout the full range of knee motion,particularly full flexion. The anterior potion of the displacementregion is large enough to ensure engagement with the IT band during fullextension, yet to avoid contact between the anterior edge and thepatella or associated tendons.

As described earlier, the displacement portion 5014 can be configuredand dimensioned to vary the displacement of the tissue duringflexion/extension, minimize contact with underlying tissue etc. Forexample, the posterior edge 5006 of the implant (also 5020 in FIG. 50Band 5045 in FIG. 51) may be elevated higher relative to the underlyingtissue compared to the posterior edge 706 of the embodiment of FIGS.18A-D. This additional elevation could accommodate more tissue under theimplant and minimize any soft tissue impingement duringflexion/extension. In one embodiment, the gap between the posterior edgeof the implant and the underlying tissue is preferably at least 1 mm,more preferably at least 3 mm, most preferably at least 5 mm, whenimplant 5000 is implanted at the target location on the femur. Toachieve this higher elevation, the posterior portion 5020 may be curvedat a higher radius than the anterior portion 5022, as shown in FIG. 51.Alternatively or additionally, the posterior edge 5045 may be bent orcurved upwardly away from the underlying bone.

Similarly, in one embodiment, the anterior region (5030) of thedisplacement portion can be contoured to minimize any lateralmaltracking of the patella during high flexion, as shown in FIG. 50D.The anterior distal surface (5030) of the displacement portion can beshaped so as to minimize any risk of IT Band irritation by ensuring alarger contact surface between the implant and the IT Band during highflexion. In another embodiment, the posterior distal edge 5021 in FIG.50B (also 5035 in FIG. 50D and 5040 in FIG. 51) can be rounded off andextended toward the underlying tissue/bone far enough so that the ITBand is not exposed to an implant “edge” during flexion, while avoidingany contact with the underlying tissue.

The implants of the present invention are subject to varying loadsduring gait due to the flexion/extension of the knee as well as thealternating weight-bearing role of each limb during gait. Additionally,the load applied on the implant due to the tissue crossing the lateralsurface of the implant depends on whether the individual is walking,jogging, running, climbing stairs etc. In one embodiment, the implant isconfigured to be rigid through the entire range of lateral loads suchthat the displacement portion of the implant remains substantiallystationary relative to the femur to which the implant is anchored. Therigidity of the implant could be altered by choice of material,increasing the thickness of the entire implant or increasing thethickness of certain regions of the implant. In another embodiment, theimplant may be designed to provide some flexibility at the higher loadsexperienced during running or climbing stairs. The flexibility of theimplant could result in the displacement portion of the implant bendingcloser to the lateral condyle at higher loads. For example, FIG. 52 is across-sectional view of an exemplary implant of the present inventionshowing two different possible thicknesses for spanning section 5201.The implant is anchored to bone through the fixation portion 5210. Thedisplacement region of the implants 5220 is connected to the fixationportion through the spanning section 5201. Spanning section 5201 may bethicker or thinner (as shown at 5202), allowing the rigidity of theimplant to be selected to provide the desired degree of deflection as itis subjected to a load due to the IT Band crossing the displacementsection 5220. The thickness of the spanning section could be varied tohave a rigid implant or a flexible compliant implant in the range ofmechanical loads on the displacement portion. Similarly, the thicknessof the entire implant could be varied to have a rigid implant or aflexible compliant implant.

FIG. 54 describes an alternative embodiment of the device for lateraldisplacement of tissue from the lateral condyle of the femur. Implant5403 has a fixation portion located somewhat more distally than in otherembodiments, with at least one fixation surface 5401 configured to reston the lateral condyle. These distal fixation surfaces may be directlyunder or just proximal (superior) to the surface of the displacementportion that engages the IT Band, but are still proximal to theattachment of the lateral collateral ligaments (LCL) and other importanttissues which attach to the more distal area of the lateral condyle. Itis anticipated that these distal fixation surfaces of the device wouldbe shaped to match the typical shape of the lateral surface of thecondyle. The fixation surfaces might also be located towards theanterior and posterior edges of the device, to maximize stability of theimplant under varying loads. This design may have several advantages.First, by locating the fixation surface(s) 5401 more distally, closer tothe displacement surface of the device, the bending stresses on thespanning section of the device are much lower. This could give thedevice an additional margin of safety in stress and fatigue loading, orallow the device to be made thinner, or allow the device to be made froma lower-strength material. For example, this device or portions of itmight be molded from PEEK (polyetherketone) rather than metals such astitanium. Second, this device may be more stable. Since the condyle ismuch wider in the anterior-posterior direction than the femoral shaft,the device will have a much wider, more triangular footprint with lowerpotential twisting stresses. Third, the device may have a shorter shaft(5403) compared to the shaft in other embodiments of the presentinvention (5402). Since the fixation surface is much nearer to thetissue displacement surface, the cantilever forces tending to raise theproximal end of the device will be lower, and the proximal end of thedevice can be shortened accordingly. This might enable the device to beimplanted through a smaller incision. Fourth, since the distal fixationsurfaces are located directly on the lateral condyle, the displacementof the displacement surface relative to the surface of the lateralcondyle will be a much more predictable.

FIGS. 53 A-C show a further elaboration of the design described in FIG.54. Although the distal fixation surfaces of the implant 5301 in FIG.53A might be located near the anterior and posterior edges of theimplant for maximum stability, it may not be necessary to locatefixation screws in those same areas. For example, if the surgicalincision is made along the posterior edge of the ilio-tibial band (ITB),it may simplify the surgery to place the fixation screws generallynearer to the posterior edge of the device as shown in FIG. 53A.

In order to accommodate the variation in femur shape from one patient toanother, it may be preferable to design in some flexibility to theorientation of the fixation surfaces of this device. FIG. 53B shows onemethod of providing this flexibility. In FIG. 53B, the fixation surfacesare made of separate elements or feet 5302 that rotate or are otherwisemovable relative to the implant 5301. Screws extend through holes in thefixation portion of the implant and through holes in the feet 5302, butthe holes through the feet are somewhat slotted, to accommodate rotationof the feet relative to the implant. This figure also shows therelationship of the device to the ilio-tibial band (ITB) and the lateralcollateral ligaments (LCL).

The interface between the device and the feet is shown in thistwo-dimensional drawing as arcuate. In three dimensions, this interfacemight be cylindrical, or it might be curved in the anterior-posteriordimension as well, following the general curve of the femoral surfaceand the device in the anterior-posterior direction. Alternatively, thesefeet might be independent of one another, with a generally sphericalinterface relative to the device.

While the feet shown in FIG. 53B might be separate and independent partsfrom the device, this might make it difficult to hold all of the partsin place during the implantation procedure. Therefore, it might bepreferable to have the feet 5302 coupled to the device 5301 while stillenabling relative sliding or rotation. One embodiment is shown in FIG.53C. In this embodiment, the slots in the feet have a countersink fromthe bottom side, and a collet or hollow rivet 5303 is inserted throughthe bottom of the feet with a press-fit into the hole in the device.This collet keeps the feet from falling away from the device, whilestill permitting the desired rotation of the foot and the screw.

FIG. 55A-C shows an additional prosthesis to improve cosmesis inaccordance with yet another exemplary embodiment of the presentinvention. Displacement of soft tissue around a joint could result in anunsightly bump. For example, displacement of the patellar tendon byimplantation of a device under the patellar tendon just superior to thetibial tuberosity could create an unsightly bump. FIG. 55A illustrates apatellar tendon displacement device (5501) like that described inconnection with FIG. 9, with fixation portion 5502, spanning portion5503 and displacement portion 5504. The tibial tuberosity 5505 andpatellar tendon 5506 are also shown. In one embodiment, apyramidal-shaped prosthesis (5507) positioned on the anterior surface ofthe tibia distal to and above the tibial tuberosity may be implanted toreduce the “bump” and improve cosmesis. As shown in FIG. 55B, prosthesis5507 may be concave on its lower side to match the surface of the tibia,and wedge-shaped as to have a low profile on its caudal end and higherprofile on its cranial end. When implanted prosthesis 5507 may slopeupwardly (ventrally or anteriorly) from the bone surface at the caudalend of the prosthesis up to the level of displacement of the patellartendon at the cranial end of the prosthesis. The prosthesis could thusprovide a smooth anterior tibial ridge leading directly to there-positioned patellar tendon. The prosthesis could be made of a rigidplastic or metal, but it could also be manufactured from a slightlydeformable material such as a silicone, urethane, or other implantableplastic. It might also have a composite construction, with a strongerelement on the posterior surface against the tibia for secure fixation,and a softer anterior surface. The anterior surface might preferably bemade of a plastic which could be sculpted by the surgeon at the time ofimplant to give the most aesthetically pleasing final appearance. Theprosthesis would be made of highly biocompatible materials, optimizedfor supporting the long term health of the skin and other surroundingtissues. This might be optimized by using materials with a poroussurface into which the surrounding tissues grow. The prosthesis could beaffixed directly to the tibia with screws, adhesive or other attachmentmeans, and may have appropriate coupling means for fasteners, e.g. screwholes 5509. It might also be designed for attachment to the fixationportion 5502 of the displacement device 5501. Further, prosthesis 5507may be an integral part of displacement device 5501, or may be fixed tothe displacement device with adhesive, screws or other fasteners, asshown in FIG. 55C. This might make it easier to implant and fix theprosthesis through the same incision which is used to place thedisplacement device.

In another embodiment the device shape could be optimized by the surgeonat the time of implantation. It may be shaped to cover the fixationportion of the displacing implant, or it could be placed beside it.

FIGS. 56 A-D illustrate an exemplary embodiment of an inserter device ofthe present invention which can be used to manipulate and holdprosthesis of the present invention in place during the surgicalimplantation process. This device (5601) utilizes two pins 5602 whichcan be placed through any two of the screw holes in the prosthesis. Theymay be angled slightly together, to prevent the pins from sliding out ofthe holes during manipulation. The device is designed with one pinattached to an inner rod 5603 and one pin attached to outer shaft 5604.The proximal end of shaft 5604 is attached to handle 5605, and theproximal end of rod 5603 is threaded and has threaded knob 5606 screwedonto it. A flat or keyway on rod 5603 prevents it from rotating relativeto shaft 5604. Therefore, clockwise rotation of knob 5606 pulls the twopins closer together, and counter-clockwise rotation of knob 5606increases the space between the two pins. Completely unscrewing knob5606 allows the rod 5603 to slide completely out of shaft 5604, for easeof cleaning and complete sterilization.

During implantation, the surgeon can use the device 5601 to grasp thedevice from a wide variety of angles, depending upon which pair of holesis selected. In FIG. 56A, the device is angled superiorly and laterally.In FIG. 56B the device is positioned superiorly. FIG. 56C shows aclose-up of the device in FIG. 56B as the pins approach the screw holeson the prosthesis. FIG. 56D shows a close-up of the device in FIG. 56Awith the pins locked into the screw holes of the prosthesis.

The device might preferably be at least long enough for the surgeon tohold it during fluoroscopy of the knee and implant, without exposing thesurgeon's hand to X-Rays. Once the surgeon has confirmed usingfluoroscopy or other techniques that the device is properly positioned,the surgeon can place Kirschner wires or bone screws to permanentlyattach the device to the femur. Once a few K-wires or screws have beenplaced, the device can be loosened and removed, and additional screwscan be placed in the holes previously occupied by the pins 5602 of thedevice.

FIGS. 57A-B show an alternative embodiment of an inserter device 5700that grasps the edges of the shaft (fixation portion) of the prosthesis5701. Inserter 5700 has opposing arms 5702 forming a channel 5704configured to slide over the shaft of the prosthesis 5701. The devicecould be placed over the prosthesis at the proximal end of the shaft,and then advanced distally until the device firmly grasps the shaft.This device might alternatively have a mechanism that allows the jaws tomove apart from one another, so that the device could be removed withoutthe need to slide it proximally along the tapered shaft.

FIGS. 58A-B show an exemplary embodiment of a dissection device 5800that is shaped to enable proper dissection of the tissue pocket in whichthe prosthesis of the present invention is placed. The ilio-tibial bandtissue commonly has small adhesions to the underlying tissue, and thisdevice could be manipulated to free those adhesions. Device 5800 has ashaft 5802, handle 5804 and a flat blade 5806 disposed at an anglerelative to shaft 5802 such that blade 5806 can be positioned parallelto a lateral surface of the femur with handle 5804 in a suitableergonomic orientation for manipulation by the surgeon.

FIGS. 59A-B show an exemplary surgical procedure to implant theprosthesis of the present invention on the lateral condyle of the distalfemur. The patient is placed in a lateral position and the limb ismaintained at full extension. A prosthesis is then placed on the surfaceof the lateral condyle. Using fluoroscopic imaging and bony anatomicallandmarks, the position of the prosthesis is adjusted. Using a skinmarker, a line (5901) is then drawn along the fixation shaft of theimplant. Using manual palpation to identify the posterior edge of the ITBand, a skin incision (length-5 cm) is then made along the marked line(FIG. 59B). The incision is then extended down to the bone, cuttingthrough the interval between the posterior edge of the IT Band and theanterior edge of the biceps femoris. Using blunt dissection or thedissection device (FIG. 58A), fibrous attachments between the IT Bandand the underlying bone are removed to create a pocket for theprosthesis of the present invention. Fluoroscopic imaging of thedissection device inserted into the tissue pocket can be used to assessthe location of the pocket, and if any additional fibrous tissueclearance is required. As shown in FIG. 59D, the prosthesis (5920) isthen attached to the insertion device (5910) and inserted into thetissue pocket. In one embodiment, the prosthesis attached to theinserter device is inserted into the tissue pocket in the anteriordirection (FIG. 59D) and then rotated in the caudal direction (FIG.59E). Insertion of the implant into the tissue pocket can be done withthe knee in full extension or in slight flexion. The location of theprosthesis is then adjusted under fluoroscopic guidance using bonyanatomical landmarks. K-wires (5930) are driven into the k-wire holes toprovide temporary fixation of the implant (FIGS. 59G-H). The inserter isthen detached from the implant and the position of the implant isconfirmed under fluoroscopic guidance. Screws are then driven into thefemoral shaft through the implant fixation portion. The knee is flexedto ensure there is no tissue impingement. The IT Band—biceps femorisinterval is sutured together and the skin incision is then closed.

As will be evident to one skilled in the art, the dimensions of theexemplary embodiments above can be altered to address differences injoint size, condyle size, level of the tissue displacement etc. as wellas to enable positioning and securing the implant at the surgical sitewhile minimizing trauma to the surrounding bone, tendons, muscles,ligaments and other anatomical structures.

While the invention has been illustrated by examples in variouscontexts, the devices of the present invention may be used to displaceany of the muscles and connective tissues around the knee to achieve atherapeutic effect. For example, the muscle displaced could be thepopliteus muscle, gastrocnemius muscle, the plantaris muscle, vastuslateralis muscle, vastus intermedius muscle, vastus medialis muscle andthe semimembranous muscle. Alternatively, the tendon associated with anyof the muscles could be displaced.

While the invention has been illustrated by examples in various contextsof treating human and animal osteoarthritis associated with forceimbalances in a joint, it will be understood that the invention may alsohave application to treatment of focal defects caused by trauma or otherreasons. In particular, pain associated with focal defects in the medialcondyle in the knee may be reduced by applying the devices and methodsof the invention to reduce loading on the medial condyle.

Alternatively, the devices and methods of the invention could be used inconjunction with other therapies used to treat focal and diffuse lesionson the condyle. For example, the device for unloading the medial condylecould be used in conjunction with microfracture or autologouschondrocyte implantation (ACI) therapy of a focal lesion on the medialcondyle.

Other applications of devices and methods of the invention include usein conjunction with meniscal repair treatment to reduce loading on themedial condyle. The contoured bearing surface for the iliotibial bandcould also alleviate pain associated with the iliotibial band frictionsyndrome. Another application includes use in conjunction with totaljoint replacement devices to alter the mechanical forces on the newjoint, thereby increasing the stability of the replaced joint andreducing the risk of implant wear. The invention may further be adaptedto displace tissues acting on various other joints so as to reduce orotherwise alter loads therein, including the elbow, shoulder, wrist,fingers, spine, ankle, interphalangeal joints, jaw or other joints. Forexample, the implants of the invention may be configured for attachmentto the acetabulum, vertebrae of the spine, scapula, humerus, radius,ulna, carpals, metacarpals, tarsals, metatarsals, talus or other bonesof the foot, among other bones.

Exemplary embodiments have been disclosed above and illustrated in theaccompanying drawings. It will be understood by those skilled in the artthat various changes, omissions and additions may be made to that whichis specifically disclosed herein without departing from the spirit andscope of the present invention.

The invention claimed is:
 1. An apparatus for treating disorders ofarticular joints, the joint being subject to forces exerted by softtissues disposed proximate to the joint with said soft tissues formingtarget tissues for treatment, the apparatus comprising a prosthesisimplantable in engagement with at least one said target tissue so as todisplace said target tissue sufficiently to alter the location, angle ormagnitude of the forces exerted by the soft tissues so as to achieve atherapeutic effect in the joint, wherein said prosthesis comprises: afixation portion including bone fixation means configured to be securedin contact with a bone forming said joint at a fixation location outsidethe articular capsule of the joint, and a displacement portionconfigured and dimensioned to extend from the fixation portion to engageand displace the soft tissue, the displacement portion having an outersurface, wherein said displacement portion outer surface is smooth andfree of holes or fixation means; wherein the fixation portion of theprosthesis is configured to be mounted to the humerus.
 2. The apparatusof claim 1, wherein the displacement portion is further configured anddimensioned to extend between the target tissue and a bone, and toatraumatically engage and displace the target tissue outwardly, awayfrom said bone.
 3. The apparatus of claim 2, wherein said bone is a boneto which the target tissue is attached.
 4. The apparatus of claim 2,wherein: the displacement portion has an inner, bone facing surface; andthe displacement portion is further configured and dimensioned toposition at least a portion of said inner, bone facing surface spacedfrom the bone.
 5. The apparatus of claim 4, wherein a portion of saidinner, bone facing surface of the displacement portion is furtherconfigured in part to rest against said bone to further support thedisplacement portion.
 6. The apparatus of claim 2, further comprising aspanning section providing a transition between the displacement portionand fixation portion, wherein the fixation portion has an inner, boneengaging surface shaped to conform to the bone at said fixationlocation.
 7. The apparatus of claim 6, wherein said prosthesis isconfigured to position the displacement portion to displace the targettissue outwardly from a natural path by distance of about 5 mm to about30 mm.
 8. A apparatus for treating disorders of articular joints, thejoint being subject to forces exerted by soft tissues disposed proximateto the joint with said soft tissues forming target tissues fortreatment, the apparatus comprising a prosthesis implantable inengagement with at least one said target tissue so as to displace saidtarget tissue sufficiently to alter the location, angle or magnitude ofthe forces exerted by the soft tissues so as to achieve a therapeuticeffect in the joint, wherein said prosthesis comprises: a fixationportion including bone fixation means configured to be secured incontact with a bone forming said joint at a fixation location outsidethe articular capsule of the joint, a displacement portion configuredand dimensioned to extend from the fixation portion to engage anddisplace the soft tissue, the displacement portion having an outersurface, wherein said displacement portion outer surface is smooth andfree of holes or fixation means; and a spanning section providing atransition between the displacement portion and fixation portion,wherein the fixation portion has an inner, bone engaging surface shapedto conform to the bone at said fixation location, wherein thedisplacement portion is further configured and dimensioned to extendbetween the target tissue and a bond, and to atraumatically engage anddisplace the target tissue outwardly, away from said bone; and whereinthe fixation portion is further configured and dimensioned to liesubstantially in a different anatomical plane than the displacementportion when secured at the fixation location.
 9. An apparatus fortreating disorders of articular joints, the joint being subject toforces exerted by soft tissues disposed proximate to the joint with saidsoft tissues forming target tissues for treatment, the apparatuscomprising a prosthesis implantable in engagement with at least one saidtarget tissue so as to displace said target tissue sufficiently to alterthe location, angle or magnitude of the forces exerted by the softtissues so as to achieve a therapeutic effect in the joint, wherein saidprosthesis comprises: a fixation portion including bone fixation meansconfigured to be secured in contact with a bone forming said joint at afixation location outside the articular capsule of the joint, adisplacement portion configured and dimensioned to extend from thefixation portion to engage and displace the soft tissue, thedisplacement portion having an outer surface, wherein said displacementportion outer surface is smooth and free of holes or fixation means, anda spanning section providing a transition between the displacementportion and fixation portion, wherein the fixation portion has an inner,bone engaging surface shaped to conform to the bone at said fixationlocation; wherein the displacement portion is further configured anddimensioned to extend between the target tissue and a bone, and toatraumatically engage and displace the target tissue outwardly, awayfrom said bone; and wherein the displacement portion lies substantiallyin an inclined plane, said plane being inclined outwardly with respectto the fixation portion.
 10. The apparatus of claim 9, wherein: thedisplacement portion has a substantially round profile lying in saidinclined plane; and the displacement portion outer surface issubstantially convex in an outward direction with respect to saidinclined plane.
 11. An apparatus for treating disorder of articularjoints, the joint being subject to forces exerted by soft tissuesdisposed proximate to the joint with said soft tissues forming targettissues for treatment, the apparatus comprising a prosthesis implantablein engagement with at least one said target tissue so as to displacesaid target tissue sufficiently to alter the location, angle ormagnitude of the forces exerted by the soft tissues so as to achieve atherapeutic effect in the joint, wherein said prosthesis comprises: afixation portion including bone fixation means configured to be securedin contact with a bone forming said joint at a fixation location outsidethe articular capsule of the joint, and a displacement portionconfigured and dimensioned to extend from the fixation portion to engageand displace the soft tissue, the displacement portion having an outersurface, wherein said displacement portion outer surface is smooth andfree of holes or fixation means, wherein: the prosthesis is formedaround a first axis lying in a first plane; the fixation portion liessubstantially in said first plane with a generally elongate shapeoriented along said first axis and has first and second ends and atleast a first width; the displacement portion outer surface is a convexsurface spaced from the second end of said fixation portion in adirection along said first axis and in a direction perpendicular to saidfirst plane; the displacement portion has an inner concave inner surfacefacing said first plane, the displacement portion having a second widthgreater than the first width of said fixation portion; and a spanningsection extending between the second end of said fixation portion andthe displacement portion.
 12. The apparatus of claim 11, wherein: theprosthesis has an overall length along said first axis of between about85-115 mm; the fixation portion has a length of between about 40-50 mmand a first width of between about 12 mm and about 15 mm; thedisplacement portion has a length of about 45-60 mm and a second widthof about 45-60 mm; and an outermost point on the convex bearing surfaceis displaced from the first plane by a distance of about 10-45 mm. 13.An apparatus for treating disorders of articular joints, the joint beingsubject to forces exerted by soft tissues disposed proximate to thejoint with said soft tissues forming target tissues for treatment, theapparatus comprising a prosthesis implantable in engagement with atleast one said target tissue so as to displace said target tissuesufficiently to alter the location, angle or magnitude of the forcesexerted by the soft tissues so as to achieve a therapeutic effect in thejoint, wherein said prosthesis comprises: a fixation portion includingbone fixation means configured to be secured in contact with a boneforming said joint at a fixation location outside the articular capsuleof the joint, and a displacement portion configured and dimensioned toextend from the fixation portion to engage and displace the soft tissue,the displacement portion having an outer surface, wherein saiddisplacement portion outer surface is smooth and free of holes orfixation means; wherein: the fixation portion is formed around a firstaxis lying substantially in said first plane with a generally elongateshape oriented along said first axis and having first and second endsand at least a first width; the displacement portion having an outer,convex bearing surface and an inner concave surface, said surfacesspaced from the second end of said fixation portion in a direction alongsaid axis and in a direction perpendicular to the first axis, the convexbearing surface further having a generally arcuate shape formed around asecond axis parallel to and spaced from the first axis, the displacementportion having a width substantially the same as the first width; and aspanning section extending between the second end of said fixationportion and the displacement portion.
 14. The apparatus of claim 13,wherein: the fixation portion and displacement portions have widthsranging from about 10 mm to about 25 mm; the fixation portion has alength ranging from about 20 mm to about 50 mm; the displacement portionhas a length ranging from about 20 mm to about 50 mm; and an outermostpoint on the convex bearing surface is displaced from the first axis bya distance of about 10-45 mm.
 15. The apparatus of claim 13, wherein thedisplacement portion is positioned at an angle with respect to thefixation portion of between about 80 degrees and about 135 degrees. 16.A method of treating a shoulder joint having first and second bones, themethod comprising: fixing a fixation portion of a treatment device tothe first bone such that a displacement portion of the treatment deviceengages target tissue in a pretreatment location proximate the shoulderjoint; and displacing the target tissue from the pretreatment locationwith the displacement portion of the treatment device by a distance andin a direction selected to provide a therapeutic effect in the shoulderjoint.
 17. The method of claim 16, wherein the therapeutic effectcomprises reducing pain in the shoulder joint.
 18. The method of claim16, wherein the therapeutic effect comprises increasing stability of theshoulder joint.
 19. The method of claim 16, wherein the first bone isthe humerus.